Most mentalism/magic that you do at a distance isn't nearly as impressive if you can do it in person. But there are a few things you can do at a distance which are great. One of them is called Thought Chunnel by Joshua Quinn (it is in his Paralies book)
Basically, someone thinks of a word and you have them go through a process in their head and they end up with a completely different word. You then tell them what it is. Nothing is written down but you can still tell them what they're thinking of.
This is a video of when I performed it on the radio...http://youtu.be/sDXXJDRhDOY
You should also look for Patrick Redford's book called Heptagon. I believe it has a ton of effects you can do over the phone