I've created a little Excel tool to help analyze fantasy trades that uses ZiPS projections. It is of course intended more as a starting point, and is probably most helpful to beginning fantasy players.
You can download it from Sendspace by clicking on the link, or also here:
[UPDATE: Replaced with v1.1 to fix error pulling pitcher info, see below]
It can handle up to 5 players on each side, and consider up to 8 hitting categories and 8 pitching categories. There is a tab explaining more, and how to enter the required info in the file.
I think I have ironed everything out in the file, but any problems are run across please leave a comment and I'll do my best to fix it ASAP and upload a replacement file.