There are many various bibliometric tools. This post appeared because of the new Google service Google Scholar Citations, which can be used by anyone starting today. The advantage of this service is that it relies on a most comprehensive database, which Google compiled through its Google scholar. As of now the service does not provide much functionality, but the main things, such as a possibility to add or remove papers from your own account, serve their purpose. There is also the so-called h-index and some other statistics. I think a lot of scientists will sign their google author accounts shortly.
If a person needs more bibliometric statistics, the most powerful free tool is the Publish or Perish program.
Another public service is Microsoft Academic Search, which has some very interesting tools, such as co-author graph, or graph of citing authors. Its disadvantage is that its coverage of scientific literature is much smaller than that of Google.
There are also bibliometric services for which you need an official (paid through a university, e.g.) access. The most widely used are Web of Science, Scopus, and MathSciNet. They all (as well as the free ones) should be used with caution, because none of them are without drawbacks (the good part of the story is that they actually can be used for many purposes, cf. with the Russian site elibrary.ru, which is a complete mess).
My account on Google can be found here.