I would second that suggestion about NaNoWriMo:). Also, if you look online, there are groups that do similar events year around!
The hardest part sometimes to start a novel, is that we (at least I) tend to over-think everything. So although I am all for having structure and a plan, plot lines, characters and the such, simply to encourage the writer in you to poke his head out, you might just wanna start writing without thinking so much about it. The one time I had the chance to complete Nanowrimo, it is exactly what I did and ended up with 80 pages of a novel at the end. If you do so, do not keep on re-reading what you are writing, just keep on writing away for a while. I find it is the best way for me to get the inspiration flowing anyways.