Nope, I have'nt tried it yet. Actually I was contemplating trying out Riya, after I made the post and before I saw your comment.
Last time I was at riya.com (long time back), they did not have a open sign-up thingie.
Riya == deriving semantics out of raw content
Self tagging == semantic web
Riya is good...
who is this mottai mandai btw...
Yours truly. That was taken in Kalpakkam ages ago.