I'm on a Mac for the moment. I managed to resurrect an old PowerBook G4 15" by replacing the PRAM battery following an ifixit tear down guide. I got the battery from PowerbookMedic and it works great now.
So what's the first apps that I installed?
Yuuguu - so that I can do quick, ad-hoc screen demos
Cyberduck - so that I can use SFTP and WebDav (I'm absolutely fearful of FTP)
Skitch - It is absolutely the best screenshot tool out there
Jing - So that I can do quick screencasts
Open Source Apps (gotta stay true :))
Firefox 3.5 - Safari's nice, but I need my Firefox add-ons
Gimp - I've been jumping between this and Photoshop, here's my opportunity to try it without Photoshop to fallback on
Inkscape - Really useful vector illustration program, opens adobe illustrator and eps files
X11 for Tiger - Yup, this thing still runs Tiger and both Inkscape and Gimp need X11 to work (thanks to Chris James Martin for making this download free, so I don't have to dig up an OS X install DVD).