Adium is my favourite app. 
Use it for Jabber and MSN.
Get AdiumBook also - it creates Address Book items so all your contacts show up as their proper name and not their MSN Display name
(and, it's all integrated into Mail etc.. then)
Parallels (obviously) and Textmate are two other apps which keep me on a Mac
Pages (iWork) is AWESOME too.. you don't realise until you use it quite a bit how good it is!
I also use "ImageWell" for resizing images on the fly.
Use it for Jabber and MSN.
Get AdiumBook also - it creates Address Book items so all your contacts show up as their proper name and not their MSN Display name
Parallels (obviously) and Textmate are two other apps which keep me on a Mac
Pages (iWork) is AWESOME too.. you don't realise until you use it quite a bit how good it is!
I also use "ImageWell" for resizing images on the fly.