Excellent thread - and now it's stickified
A couple quick additions:
Under software equivalents, <a href="http://gaim.sf.net">Gaim</a> is listed as a AIM/MSN/YIM/ICQ/Trillian replacement. I'd like to also add <a href="http://kopete.kde.org">Kopete</a> to that. It, like Gaim, is included with many distros.
As an Outlook replacement, <a href="http://www.ximian.com/products/evolution/">Evolution</a> is listed. There is also a PIM program recently released for the first time by KDE called <a href="http://kontact.kde.org/">Kontact</a>. I have heard good things about it, and it is basically just a PIM implementation of already existing and good KDE programs such as <a href="http://kmail.kde.org/">KMail<a>, which is a good stand-alone E-Mail client under KDE for example.
Lastly, while Freshmeat is a great open-source software site, <a href="http://www.icewalkers.com/">IceWalkers</a> is also very good.
EDIT: Info's added above - thanks for the permission Latch
