Google Voice if you're not using google voice you should be

JotNot Scanner Pro: scan multipage documents to PDF this is a great scanning app using your iPhone camera. I've documented many a white-board brainstorming session via this app. You can also save these notes to Evernote via this app.

Evernote all of your notes accessible on the go - create voice/text/picture notes to remember when you get back to the office

Tungle - Calendar sharing & scheduling this is the best scheduling system I've used. Tungle is a web-based service that allows people to schedule appointments with you based on your availability. I use the app to update appointments while I'm away from my computer.

SugarSync I just started using SugarSync to backup my documents folder on my laptop it's nice to be able to access the files on my phone as well