Now that founder members of Truphone are no longer able to call landlines in the UK and 40-odd other countries over home, office and outside free-to-use WiFi connections for nuffink, I've started using a SIP client on my Symbian smartphone, but punting the calls via my laptop.
I didn't realise you could do this so easily under Vista - it's about the only Vista advantage over XP that I'm impressed with - but you can plug in a mobile broadband dongle and then set up an ad-hoc network using your laptop's WiFi transceiver.
This basically gives you VOIP access on a mobile phone (or a VOIP cordless) when you have your laptop operational, punting your Internet surfing data and VOIP calls across the 3G broadband connection.
Being the generous sort, I was stationed in a coffee shop at St Pancras the other evening, waiting for my unhappy shopper cheap first class ticket train back to Sheffield at 1925 hours, and didn't bother setting
up a password on my ad-hoc connection.
When I was shutting down after a 75 minute laptop session, I noticed three other people in the station - but not in the coffee shop - also piggy-backing on my WiFi.
I hope they weren't too upset when I scarpered for my train. Even if one of the cheeky monkeys was using a bittorrent client for what looked to be around half-an-hour.
S/he only gobbled 200 MB of my 3 GB monthly allowance... :)