Busta
The Busta widget is a speedy and very lightweight VoIP widget that can be embedded into your Google, Live, Pageflakes or Netvibes homepage with ease. There is also a handy Firefox extension that places Busta in your browser's sidebar for convenience. Busta is based on SIP technology, which means you can make cheap calls to landlines and mobiles on the PSTN and free calls to other devices on SIP networks.

GizmoCall
The GizmoCall widget is being developed by the same parent company responsible for Gizmo and Gizmo5, which is their mobile VoIP offering. Unlike Busta, the GizmoCall widget is far from lightweight but it is based on SIP, which means free calls to other Gizmo contacts and SIP devices as well as reduced rates to landlines and mobiles. You can easily embed a link in any blog or MySpace / Facebook or other social network profile so friends can call you. Registered GizmoCall users get 5 free minutes usage.

Jajah
The much lauded Jajah web-based VoIP service also has a very capable widget that can be dropped into your emails, blog and a variety of social network profiles including those of MySpace and Bebo. Jajah works as an intermediary; the Jajah widget lets users enter their own number and the number you want to call, Jajah calls and connects both numbers, which saves you money. Out of all the widgets, Jajah's is the most rounded and widely supported.

Jaxtr
While it may be less widely appreciated when compared to Jajah, the Jaxtr widget is a polished product. Not only can you embed the Jaxtr widget in your MySpace, Friendster, Blogger, LinkedIn profile to allow friends to call for cheap, but with Jaxtr you can also send SMS and receive voice messages. Calls to other Jaxtr users are free.

Wengovisio
The Wengovisio widget is developed by the same people who have brought us Wengophone in the past. The Flash widget can be installed on a blog or social network profile with embedded CSS and JavaScript. The best feature of the Wengovisio widget is that it is capable of both audio and visual calls, right from within the widget. Wengovisio doesn't let you call landines or mobile phones.