Hello! It's hard to really give hard facts as to what you should get because we don't know more details about what you want to do with the recording system.
However, regarding software - a great program to start with is Audacity - it's FREE and can be found here:
http://audacity.sourceforge.net/download/
It's available for PC or Mac. Also - go to
www.kvraudio.com and you can find a boat-load of free VST plugins covering just about anything you may need. VST plugins are small software applications that simulate effects like reverbs, delays, distortions, eq, etc...
Regarding the audio interface, the drivers are one of the primary factors influencing latency. Sample rate and system proccessing power are other influences. You will probably want to find an interface that has ASIO drivers - these give very low latencies in general. USB 2.0 can do mutli-channel audio (8 channels for example) - perhaps more but your system needs to be tweaked for maximum performance. Actually you should do that no matter what interface you use. Firewire comes in two basic flavors - FW400 and FW800. The latter is much faster, but the interface cards are harder to find and not too many audio interfaces are out there. If you decide to go Firewrie - check the manufacturers website for any information regarding interface cards. Most FW interfaces seem to work well with FW cards that have the Texas Instruments FW chipset...but check with the interface manufacturer to be sure.
Some manufacturers to check out: M-audio, Edirol, Mark of the Unicorn, Tascam, RME (more expensive but one of the best, IMO), Lexicon, Echo,....
Also - you can get a simple setup going using your internal sound card and a FREE ASIO interface program called ASIO4ALL - I think this is the URL for it:
www.asio4all.com This may allow you to use your computer sound card for some basic recording - enough to get you started. Mind you - it will not be as high-performance as a dedicated pro-card will be.
Once you go thru some of the free software and such you should be getting an idea of what features you like, don't like, would like to have, etc... and then start checking out the various software venders to see who hit's closest to the mark. Also - and probably more importantly - talk to your friends and see what they use. This way if you have a question you have someone you know you canbounce it off of...
Dave