SocialMeter is a straightforward little site. Paste in your URL and it gives it a score based on the number of links it finds at Google, Delicious, Digg, Reddit, Furl, etc -- 11 sites in all. (If you have a popular site, it's not quick.)
Is it any use? Well, it could be a good way to track one site across time. Otherwise, http://www.socialmeter.com/ is probably as reliable as its sources, which may be "not very".
For example, SocialMeter gives itself a low score because it doesn't find any links in Google.
According to a comment below: "The reason for this is that Google takes between one and two weeks to add new pages into its databse, so all these links in the past few days won't get shown there."
(In an earlier version of this post, I wondered if there was some other reason Google wasn't listing them, but clearly this is a far more likely explanation.)
Either way, it does point up the potential problem of comparing sites using one-off searches with SocialMeter: the sources may not always be updating at the same time and at the same rate.
