For information on using VoIP with Mobile Broadband, click here.
The 3 Skypephone S2 is the best way to take advantage of 3's free Skype to Skype calls.
It also comes with a 3.2MP camera, 50MB of internal memory, as well as a slot for a microSD memory card. You can easily switch between multiple running programs. And you can also plug it directly into your computer like a dongle, so this makes it great to use with Mobile Broadband.
You can get this phone on Contract and Pay as you Go. It's free on contract, and just £69.99 on Pay as you Go, making it affordable for use with Pay as you Go Mobile Broadband.