Well, not knowing what you have installed and what you plan to use your computer for, I can't really tell you what to get rid of
Look through each package, read up on what it is and why you might want it, and decide whether you need it or not. You can always reinstall it later if you find out you want it. See if you have multiple similar programs installed - there may be three or four web browsers installed by default; remove all but the one you like to use. If you only use Gnome, remove KDE stuff (or vice versa). If you don't plan on using your computer to host web sites, mail, ftp, telnet, ssh, or any of those types of services, you can probably uninstall apache, sshd, and similar server stuff. Remove perl, php, python, etc. if you don't plan on programming in those languages. (sometimes other software needs them, but again, you can always reinstall it later).
Look around, I'm sure you'll find stuff you don't need.