Here is the start of an FAQ for folding@home for our team.

Question: How does this work?
Ans: In folding at home, there are many different areas of research (related to figuring out diseases and to help figure out how to stop or cure them) that need computational help. The work is broken down into small pieces (work units) so that it can be given to volunteer computers around the world. Currently there about 200,000 computers from just about all countries participating in this project. Without this support, much of this research just wouldn't be possible. The work is non-profit and made public to everyone.

Qn: Will this cause me to get viruses or something similar?
Ans: This is a very secure project, everything is between your computer and their server and is highly encrypted. There are no others involved. Privacy is very strict, no information outside of the project itself is passed (not even email address). Google has done an in-depth security analysis of this project and it resulted that this was the only research project that was accepted into the Google bar. (Google has redone its Google bar but was unfortunately not compatible so Google suggested to use one of the available clients instead).

Qn: So how does it work?
Ans: After installing the client (see below for more info about clients), and answering some questions (e.g. what is your team number!!!), a project workunit is sent to your system. Your system does the calculation and then sends back the results of the calculation. Note that work units from different projects are different and cannot be compared to other project work units to see how fast it will complete it.
This, and other similar projects (e.g. SETI) are designed to work with your computer's idle time only. For example surfing on the internet usually uses just a little bit of the computer's capability (let's say 10% average), so the rest can be used for folding (90% in this case)!
You can specify how much of the idle you want left (it is called CPU usage %). I normally suggest around 80% instead of 100%. Folding goes a little bit slower, but I find that it becomes unnoticeable (and the benchmarks results are also just about identical with folding at 80% and no folding at all).

Qn: How will this affect my computer?
Ans: Folding does work the CPU harder (and so hotter), similar to when working with video files. This shouldn't have any significant impact on the computer life in just about all cases. Some exceptions are a) computers without a working exhaust fan, b) computers that are over-clocked without adequate cooling, c) computers that are chocked full of dust bunnies.
Those are many of the same reasons that folding can have trouble working on a system (see the comments below about the windows graphic client for the other main reasons). For those that do overclocking (otherwise ignore this sentence!) , prime stable isn't good enough - drop the FSB by just a little is usually all that is needed.
Adjusting the CPU usage % is also important if the computer gets too noisy while folding, or too warm, especially notebooks/laptop PCs. e.g. On my old notebook, I noticed that at 40% CPU usage the fan stays very quiet, but at 80% it is noisy.

Qn: How much electricity will this use?
Ans: The extra work above idle mean that the computer uses up a bit more power than idling. Two examples: on my old P3 computer, it is about 15 watts more than idle, on my newer computer X2 it is about 25 watts more than idle. Notebooks usually use less power, high-end system usually use more.
For my X2, running 24/7 even if it wasn't folding, at 0.06/kWh local power cost, this works out to be just over $1/month. As 95%+ of the power use goes to heat, in the winter months (5 months...) when heat produced is desired, the net cost is closer to $0.10 month. The P3 is only on a 4 hours a day average, so the cost is much lower ($0.07 per month).
Of course if use to have the computer on for 4 hrs a day and now want it to go 24hrs, then it is the difference between "off" (usually under 10 watts unless turn off by unplugging/power-bar) and full-use (for my X2 around 110 watts) so that would be much more noticeable.

Qn: There are many different programs available for download! What are the differences between them?
Ands: There are several different type of folding programs (called clients) available. Each have their own advantages & disadvantages. You only need to pick one, and you can change to a different one if you want. Here is the list:

A) The "Windows 2000/XP/Vista Graphical client" is often the first choice, but it has one significant issue for some people.
This issue is that this client uses 3D graphics to draw the molecules, Windows dislikes having two 3D programs running at the same time (including some screen savers), but it can be the graphics on the system that can be the problem. ATI 9600 series graphics are known to have serious issues (e.g. system crashes) so are not suggested with this client. For other cards, if they have a problem, it is usually a 3D graphic program (e.g. a game) trying to use the full screen that gets bumped back to a window or minimized. If that is the case, just use another folding client, or stop the folding program when using the 3D application.
A minor cosmetic problem (as some here already have noted) is that the estimate for time to completion is completely wrong whenever it starts working on a new project work unit (WU). Give it a bit of time and it should correct itself. Most WUs take at least 1 day, some can take several days.

B) Windows NT/2000/XP/Vista "No nonsense" text-only console client. Also available for Linux, BSD and older Mac PCs. This is a popular choice especially for those that are comfortable around computers. The downside is that it doesn't have a pretty interface (just text) and doesn't give easy display of how much it has completed (it is in another text file). There are however 3rd party applications to display information if desired. I'll provide more info on this client if anyone wants (or if we have a FAQ area).

C) Windows/Linux/Mac (new Macs with Intel only) SMP client. This is an intense beta client for dual core or more systems that requires the computer to be on most of the time and suggested only for those comfortable with computers.

D) PS3 client. If you have a PS3, I suggest running the folding client for it. The client works great and is very nice! And the PS3 is very powerful/fast for this type of work! If you need more info about this, let me know.

E) Windows XP/Vista GPU client. This is a high performance beta client that requires specific types of graphic cards. Right now only the X1600/X1650/X1800/X1900/X1950 series are supported. There are few issues with this client as mentioned in its FAQ. Like the SMP client, this beta client is also suggested only for those comfortable with computers.
If you want more info on any of these client, let me know and I'll help as I can (or point you to a link for more info).

More info to come
And happy 1 week anniversary to the GitP team!