Just a quick plug for a cool tool i just found the other day.
Uniextract is an open source GPL tool that supports a huge number of compressed file format types and can extract them all based on a very simple command line (or shell menu, or dialog prompt)
Written in the freeware Autoit script language, and compiled as a standalone executable this 90k character script is well written and functions as promised. If you want to run it as part of a fully automated system, there are only a handfull of source mods necessary and it recompiles easily even with no experience in the Autoit script language.
As for the actual extraction code, that is handed off to a whole slew of specialized command line apps.
All in all, if you want a simgle tool to extract a ton of different formats, this is the best tool i have found for the job yet. Very appreciative of his work (and everyone who write the exectractors) and that they released it open source to boot!
If your in the market for a tool like this, check it out
One more note...if you have to use it as part of an automated system you will run into trouble with password protected files. Zip and rar, commandline apps will request the password on the console which means program hang. Also if you have to support winzip AES encrypted files you are sol. Turns out I cant use it for my project, oghh well.