Importing contacts from Gmail, Hotmail, etc.

[eluser]charlieD[/eluser]
Hi all,

I'm working on an 'invite friends' application like you get in social networks - i.e. you enter your contact details for your mail accounts (Gmail, Hotmail, Yahoo mail, Facebook) etc. and the site then imports them, lets you choose who you want to send an email to, and handles the invite side of things.

There seem to be open APIs for Gmail, Hotmail and Yahoo but rather than handle these all separately are there any good classes out there that help handle this?

Thanks