Google Drive: Yeah, the client is Intel-Only, but you can run a TenFourFoxBox for that and/or Dropbox when you need to grab/send something. I use this exact scenario for Dropbox.
Web Browsing: The awesome TenFourFox or the equally good Leopard Webkit
Facebook: Using TFFB would be the best bet again, as would be logging into their mobile site. Mobile seems to work a lot easier on PPC than the "real" site.
Spotify: Believe it or not, I don't use it!
Thanks! Mobile facebook works great. Do you know where I can get a old copy of Garageband for Tiger? Also Photoshop CS2/CS3/CS4? =)