Today, flaphone (formerly Flashphone) announced that users of their Flash VoIP application can now make a call from flaphone to skype. You simply need to enter sip:skype_username@skype after selecting "none"(global)" for the SIP account. I should mention that flaphone supports multiple SIP credentials, which is a really nice feature. I've been testing flaphone for several weeks now and have been meaning to write up their cool Flash-based VoIP application.In any event, for my first test call I entered sip:tomkeating@skype and pressed the call button. The call was initiated and the call quality was superb!
You can also use this SIP-to-Skype feature for flaphone's CallMe widgets that you place on your website.
Similarly, Gizmo5 recently launched OpenSky which also enables SIP-to-Skype dialing. However, Gizmo5 calls are free only up to 5 minutes long. For longer calls they are offering a paid service. There is no such restriction that I am aware of with flaphone.
By leveraging Flash, flaphone is cross-platform, has minimal download time, and you can run it from any browser. That and the fast that it supports SIP-to-PSTN calling, SIP URI dialing, and SIP-to-Skype calling, means this is one VoIP app you should check out!
