There’s a new beta version of Skype available, with the (possible) incentive of cheap SMS text messages. It looks like it’s 5.5p per txt within the UK, which may compare favourably with your mobile tariff. Or may not, depending. Still a nice gesture, though.
Once you’ve upgraded, you might want to try something called ‘Skypecasts‘, which look like big audio chatrooms / lectures (up to 100 participants). The sessions currently on offer don’t look especially inspiring, but it’s an interesting concept. How you ‘chair’ a discussion of 100 people is, initially at least, a mystery to me.