vote for Bobsled (Facebook Calls) for Maemo Contacts and Conversations
 

I don't know what the chances of this actually happening are, but I put in a request to have a version of T-Mobile's Bobsled (by Vivox) made for Maemo. You can vote for it here:

http://bobsled.uservoice.com/forums/...nd-conversatio

The default download that facebook served me seemed to install as an add-on in firefox, so i havent tested yet to see if firefox on maemo can utilize it in the browser. but a C&C plugin would be easier to use i think.