The following 'free' resources may help you in determining the impact of your research:
"There is a pressing need to improve the ways in which the output of scientific research is evaluated by funding agencies, academic institutions, and other parties... The Journal Impact Factor is frequently used as the primary parameter with which to compare the scientific output of individuals and institutions. The Journal Impact Factor, as calculated by Thomson Reuters, was originally created as a tool to help librarians identify journals to purchase, not as a measure of the scientific quality of research in an article. With that in mind, it is critical to understand that the Journal Impact Factor has a number of well-documented deficiencies as a tool for research assessment."
To read the full statement and signatories to a set of recommendations, referred to as the San Francisco Declaration on Research Assessment, go here.