They are only $7/yr from Godaddy (so under 4 quid for us brits). ablogsoup.com isn't available, but you could get the .net or .org or whatever country tld would work (eg .co.uk for me).
Even if you decide not to get your own hosting ($5+/month), a domain is always a good plan as if you fall out of love with blogger at anytime you can quickly move to another service and take your users with you.
I would second the warning against hosted forums though
tim, i did actually have that domain, ablogsoup.com, but did not renew it this year. I have thought about getting the .net or .org though. thing is, i have no idea how to use ftp, and attempting to learn did no good. I just had no idea how to use ftp, i just couldnt figure it out.