I built a web-based comic book collection app using the comic-vine APIs as a primary data source.
Check it out at http://www.comics-exchange.com/application
It's free to use and you can create a collection, create a wishlist and find other users that have issues that you want.
It's in beta testing, so please provide feedback if you run into any issues, or if it is missing features that you would like to see.
Thanks to the Whiskey Media guys for making the API available!