Hi all!
Calls have become very cheap nowadays - Free if you and the other user use Skype etc!
For traditional phone calls, I use Swiftcall, a relatively 'high' monthly access charge of £19.99 / month but has 0207 and 0800 access, free calls for the UK at anytime and free calls to the USA/Canada including of course mobiles. I think this package also includes calls to around 25 Euro countries as well. A very 'high' fair usage policy, 75 minute call cutoff and then just redial. Call quality is simply the 'best' as it of course uses copper/traditional cables.
Vonage is similar - but uses the IP protocol, excellent call quality and a cheaper access charge. However, as I've called from my Swiftcall account to a Vonage user in the US - I'd say theres much more brief cutouts, some longer 10-20 seconds 'static noise' gaps and occasionally dropped calls etc. For me, just enough to delay with getting the vonage option for now.
If of course those slight drawbacks dont matter - go for the Vonage option and save some money!
Hope this helps ! Cheers! DtM! West London & Slough UK!