As there is a constant stream of new and valuable resources being put on the internet, I'm dedicating this topic for anyone to post any links to free valuable resources that they have/know of, and I shall also contribute new stuff to it as well.
May as well start off with this brand new little goodie:
http://stephanus.tlg.uci.edu/lsj/#eid=1&context=lsj" onclick="window.open(this.href);return false;
This is the new online version of my favourite, and probably best, Greek-English Lexicon: The Liddel-Scott "A Greek-English Lexicon", also commonly known as the LSJ (J referring to Henry Jones, who revised it). More info about it is on Wikipedia: http://en.wikipedia.org/wiki/A_Greek-English_Lexicon" onclick="window.open(this.href);return false;