Quarkbase is a free tool to find complete information about a website. It is a mashup of over 30 data sources and many algorithms gathering information from Internet on various topics like social popularity, traffic, associated people, etc. e.g. http://www.quarkbase.com/show/microbiologybytes.com
The simple linear regression model considers the relationship between two variables and in many cases more information will be available that can be used to extend the model. For example, there might be a categorical variable (sometimes known as a covariate) that can be used to divide the data set to fit a separate linear