Check out extundelete, application for undeleting files on ext3. Please note that in typical system there is rather many automatic write operations to disk, and probability for losing deleted files (as those disk areas are overwritten) is high.
Typically you want to remount your filesystem as read-only or boot from live-CD or similar to prevent overwriting, if you want to successfully restore any files.
Another maybe useful (but less so) link is this tutorial for recovering files. Method described in there is rather complex.