At most times: in addition to the usual Mac stuff including Mail, Calendar, Reminders and Safari: an
IDE, 2 instances of PostgreSQL,
Tomcat, 2 or 3 instances of the Play! server, Photoshop, Illustrator, Bridge, 5 or 6 terminal windows, and a text editor. Sporadically: iTunes, iPhoto, InDesign, OmniGraffle, Evernote, Preview,
Word, Numbers, and so on.
Oh, and sometimes a Parallels Desktop loaded with Windows 7 for IE
testing.
8GB got gobbled up pretty fast!