This is something I very much miss from desktop IM clients.

To do this, Meebo would either have to bounce files through Meebo servers (costly for them), or offer an installable direct-connect application or browser plug-in.

Unfortunately, with a direct-connect application, users without the administrative privileges to install software would not be able to share files.

Alternatively, Meebo could partner with a file hosting service like http://www.yousendit.com/ or http://www.senduit.com/ and offer a simple and convenient link for sharing files.

I favor the combination of a standalone application that direct-connects two users, and a widget powered by a file hosting service.