I've discovered Stessa.com based on a recommendation from a client and recommend it for many investors. It's real good for doing basic bookkeeping as well as providing a number of other useful financial tools.
The basic bookkeeping is free, allows you to track income and expense by property, and gives you the ability to run several reports. Please check it out.
I've also attached a useful article from Stessa which discusses rental property tax considerations. I agree with most everything they are saying. Please check it out too.
Don
