Developers itching to test drive Microsoft’s latest instant messenger can now bid for an invitation to join the test program on eBay.

Some 70 invitations to the Windows Live Messenger 8 beta test program have been posted on eBay, with many sellers looking to make around $25.00 per invitation.

The beta program has been made available to a limited audience of private testers, although program participants have been issued with a number of invitations for friends, family or “the highest bidder.” Microsoft’s Windows Live Messenger team said the program’s size was restricted to limit the hits on its back-end servers.

Windows Live Messenger is the updated version of MSN Messenger, re-branded to fit Microsoft’s recently announced “Live Software” Web 2.0 strategy. Windows Live Messenger features a contact list for up to 600 people, PC-to-PC phone calls and folder sharing.