I'm looking for a way to make website thumbnails as you commonly see in a lot of social sites. However, I don't want to use a preexisting service. From my understanding is it's kinda a pain in the *** to do, but my understanding is limited (hence the question). This is especially because my servers are not local (hosted on godaddy atm) and am not sure I can do this without my own servers. Anyhow, so I'm wondering if it is possible and anybody has experience in doing it or knows how to do it, again without a preexisting service. Thanks

AFAIK, there is no way how to do it on shared web hosting w/o 3rd party services.

You could use imagegrabwindow() on windows machine or write some scripts for capturing screenshot on linux, but it requires graphical enviroment or some specific command line tools. Either way you would need access to server configuration.