I have 8 invites. As I was lucky enough to be invited by Mr Twist on this very forum, I will invite the first 8 STWers to send me their googlemail (or gmail) addresses (a gmail/google mail log-in is required by wave)
If you have invites then there is a "Wave" in your inbox with the title "Invite others to Google Wave"
in that case then I haven't got any yet. I was invited from another forum middle of last week but now I know what to look out for I'll keep checking and spread the waves about
at the moment, it's pretty limited, but I can see the use of it, we organise our group rides on it, it makes it easier to read and share things, better than emails… only problem at the moment is, that ppl need a gmail account, so some are reluctant to have another email address