[RTuesday]

GT-sim is another with an Isle of Man number. I like the fact it is postpaid (and SMS is currently free), but it's only free incoming in one country which would limit it for some people.

Cheapest way to call an IoM mobile via a US number: set up a skype-in number in the US, and call-forward it to the IoM number. Currently charged at the Skype world rate (2.1c/min). Disadvantages: that's a billing error, so won't last, the forwarding is slow (many rings), the quality is often poor and there is a $3/mo fee for the Skype in number.

Next alternatve: ipkall.com or freedigits.com US number (both free), forwarded to the SIP address of a free account at voipfone.co.uk (I use this a lot, works well). Forward the voipfone.co.uk number to the IoM mobile for 8.4p(15c)/min, prepaid in 5 pound chunks, no monthly fees. I don't think any other VOIP companies offer anything below 15c/min for UK mobiles, and most have monthly fees.

So, this gives a US number to call, and costs you 15c/min to receive calls in the countries that an IoM roaming mobile is free to receive in. It's worth getting a US number, as the cost of calling a UK mobile from a normal US carrier, can be very expensive on basic plans (e.g. $1.46/min on Qwest).