Evernote Hello (free)
This app allows you (or the person you just met) to create a profile of the people you meet on your phone. Photo, name, info, notes regarding the person, relationship, how you met, etc. Forget business cards that get lost or thrown away (although I will still be taking those archaic things too).
Expensify (the free version)
An app that allows you to track your business expenses quickly and easily with your phone. You can scan your receipts and if you choose, it can create an expense report for you (but I think you have to pay for the version that does that).