View source for Current situation, what is possible in SL till now?

According to Wikipedia, SL gives you the following possibilities:
Residents
The basic avatar is human in appearance, but avatars may be of either sex, have a wide range of physical attributes, and may be clothed or otherwise customized to produce a wide variety of humanoid and other forms. A single person may have multiple accounts, and thus appear to be multiple Residents (a person's multiple accounts are referred to as alts). However, the use of additional accounts requires the Resident to register them and pay a small fee. Also, a single Resident's appearance in Second Life can vary dramatically at will, as avatars are easily modified.

Communication and transport
Within Second Life, there are two main methods of text-based communication: local chat, and global "instant messaging" (known as IM). Chatting is used for public localised conversations between two or more avatars, and can be "heard" within 20 m. Avatars can also 'shout' ('audible' within 100 m) and 'whisper' ('audible' within 10 m). IM is used for private conversations, either between two avatars, or between the members of a group. Unlike chatting, IM communication does not depend on the participants being within a certain distance of each other
The most basic method of moving around is by foot. To travel more rapidly, avatars can also fly up to about 170 m over the terrain (meaning 270 m if ground level is 100 m, 180 m if ground level is set to 10 m) without requiring any special equipment, and with scripted attachments there is currently no limit to how high an avatar can fly (although once past several thousand meters, the rendering of the avatar mesh starts to be affected).

Avatars can also ride in vehicles; many vehicles are available — there is a basic go-kart contained in the object library and there are many Resident-made vehicles available freely and for purchase including helicopters, submarines and hot-air balloons. Airborne vehicles can fly up to 4096 m high (the maximum altitude allowed for any object).

For instantaneous travel, avatars can teleport (commonly abbreviated to "TP") directly to a specific location. An avatar can create a personal landmark (often called an LM) at their current location, and then teleport back to that location at any time, or give a copy of the landmark to another avatar.

There are some external websites that allow Residents to locate each other from outside of the virtual world, and SLurl.com allows external links through the Second Life World Map to locations in-world.

Economy and real estate
Second Life has its own economy and a currency referred to as Linden Dollars (L$). Though the exchange rate fluctuates, as of February 2007 it is reasonably stable at around L$ 270 to one US dollar. 

Residents create new goods and services, and buy and sell them in the Second Life virtual world. There are also currency exchanges where Residents can exchange US$ or other real world currencies for L$. These exchanges are open markets, except that Linden Lab sometimes buys or sells Linden dollars to attempt to keep the exchange rate relatively stable. A small percentage of Residents derive net incomes from this economy, ranging from a few hundred to several thousand US$ per month, while a larger percentage derive a gross income large enough to offset most of their expenditures in L$. The currency has become the subject of concern in economic circles in regard to possible taxation.
 
Premium members can own land (up to 512 m² without additional fees). Owning larger areas of land incurs an additional fee (which Linden Lab calls "tier") ranging from US$5 a month up to US$295 a month for an individual island. Linden Lab used to sell land at a reduced rate to new Residents in small 512 m² lots (e.g., 16 by 32 meters) through its First Land program, but this program ended on 20 February 2007 as the land was often being quickly resold at a profit rather than kept by the Resident. It also sells 16 acre (65536 m2) regions. Once a Resident buys land he or she may resell it freely and use it for any purpose. The only exception to this is land purchased in "private sims" or "private islands", which are governed by Residents and not Linden Labs. These private islands have what are called covenants that may restrict use of the land, such as prohibiting any commercial activity, or even resale of the land itself.

Creation and copyright
One of the distinguishing characteristics of Second Life is that the Residents, not Linden Lab, create most of the content of the world. The Resident avatars are one example of such user-generated content.

There is a 3D modeling tool in Second Life that allows any Resident with the right skills to build virtual buildings, landscape, vehicles, furniture, and machines to use, trade, or sell. This is a primary source of activity in the economy. Any Resident can also make gestures from small animations and sounds from the standard library. Outside Second Life, Residents can use various graphics, animation, and sound tools to create more elaborate items, and upload them into the world. Once the creation is in the world of Second Life, the system makes efforts to help protect the exclusive rights of the content creator. When objects are created (or instantiated) in-world and then transferred to the Resident's computer, they are said to "rez" — a reference to the Disney movie Tron. This also appears in the environment's internal scripting language, where the command to create an object is llRezObject().

Second Life also includes a rich and powerful scripting language, called Linden Scripting Language, or LSL. This is used to add autonomous behavior to many of the objects in Second Life, such as doors that open when approached.

A Resident who creates some item and the Resident that owns an item retain certain rights, simulating and in some ways enhancing the copyright available in the real world. The creator can mark an item as "no copy," which means that no copies of it can be made by others, "no mod," which means that others may not modify the item's characteristics, and "no trans," which means that the current owner may not give it to another. In addition, these rights can be set for future owners. That is, an item that is copyable and transferable might become non-transferable once it has been transferred. For example, A may create some item and give it to B. B can give to as many Cs as he wishes, but the Cs will not be able to give.

Live music performances take place in Second Life, in the sense that of vocal and instrumental music by Second Life Residents can be provided from their homes and studios. This is played into microphones, uploaded to audio streams, and played in-world for the enjoyment of other Residents. This started with performances by Astrin Few in May 2004 and began to gain popularity mid 2005.[31] Linden Lab added an Event Category "Live Music" in March 2006 to accommodate the increasing number of scheduled events. 

 
Businesses and organizations in Second Life
A combination of Linden Lab granting Second Life Residents the copyright over their content, and legal trading of the in-world currency "Linden Dollars" (L$)has encouraged the creation of solely in-world businesses, the creation of legally registered companies that were previously solely in-world, and the in-world participation of previously unrelated companies and organisations.

In early 2007 the Swedish Institute stated it was about to set up an Embassy in Second Life. The Swedish Minister for Foreign Affairs, Carl Bildt, stated on his blog that he hoped he would get an invitation to the grand opening. 

Education in Second Life
Second Life has recently emerged as one of the cutting-edge virtual classrooms for major colleges and universities, including Harvard, Pepperdine, Ball State, New York University and Delft University of Technology. Second Life fosters a welcoming atmosphere for administrators to host lectures and projects online, selling more than 100 islands for educational purposes, according to a New York Times article. The article quoted Rebecca Nesson, an instructor at Harvard who brought her Legal Studies class to Second Life in the second half of 2006. "Normally, no matter how good a distance-learning class is, an inherent distance does still exist between you and your students," she says. "Second Life has really bridged that gap. There is just more unofficial time that we spend together outside of the typical class session."