Flashphone is a web-based SIP softphone, while gtalk2voip lets you make or receive calls to/from all SIP phones and SIP services, including Yahoo Messenger, MSN Messenger, and Google Talk. Both Flashphone and gtalk2voip are free. Now combine the two and you can make free web-based Flash calls to Yahoo Messenger, MSN Messenger, and Google Talk (gtalk) users.

According to the Flashphone blog, "For example, if someone is online in Gtalk and you want to call him from flashphone you just need to enter SIP URI like sip:google_usernam[email protected] and gtalk user will see incoming call. You also can easily call to flashphone from gtalk via gtalk2voip, add contact like [flashphone_login][email protected] and call to this contact, flashphone will ring if user online."

Pretty sweet!

image of Flashphone during one of my tests: