Still wondering what to get that Microsoft enthusiast for the holidays? Microsoft's Windows Live team has an idea - an invitation to a limited beta of Microsoft's next-generation IM client, Windows Live Messenger.Microsoft is auctioning off invitations to the private beta release of the forthcoming client on eBay's auction site, according to a posting on the Windows Live team's blog."Xbox 360 is not the only thing in short supply this holiday season," according to a posting on the Windows Live blog. "So like Xbox, Windows Live Messenger beta invites are appearing on eBay."The auctions can be found here.While many of the other Windows Live services and Web-based applications, such as Windows Live Local and Windows Live Mail, are available in public betas, Windows Live Messenger is by invitation only.Windows Live Messenger, part of Microsoft's Live Software plan to offer a set of Web-based services and applications, will eventually replace the current Microsoft IM client, MSN Messenger. The next version of MSN Messenger will be rebranded Windows Live Messenger 8.0. Windows Live Mail also is expected to take the place of MSN Hotmail in the future.The eBay auction sites for the beta invitations provide a screen shot of the upcoming IM client, which promises to allow users to more quickly and easily share files such as photos and music, as well as make PC-to-PC voice calls with other Windows Live Messenger users, according to Microsoft. The client also will have a new user interface and allow users to message buddies even when they are offline.At the time this article was written, the highest price for one of the Windows Live Messenger invitations was $20. The Windows Live team has started a pool to guess what the highest selling price will be for one of the invitations, according to the team's blog.