Google Scholar Citations
Google Scholar offers a free citation service that creates academic profiles. This provides a simple way for authors to keep track of their citations, to find out who is citing them and provides the author with a H index. An author can also make their profile public so that it shows up when somebody types in his/her name. Scholar metrics basically cover a five year period only. Google will only index websites that follow their inclusion guidelines, selected conference articles in Computer Science/Electrical Engineering, and preprints from arXiv (science), SSRN (Social Sciences), NBER (Economics) and RePec (Economics). They tend not to cover articles from smaller publications.
While the service is free it has limitations. The data can be muddy and prone to duplication, there can be mismatched papers i.e. the wrong author matched to a paper, and it fails to take into account the new ways scholars communicate. It is worth ensuring that your profile is correct, that the correct articles are attributed to you and that your profile is public so people can see it. While Google will automatically update your profile (once you have selected that as an option) it is worth regularly checking the information.