geeksblog.com - its more community friendly plus you could open up the option of having guest bloggers, fellow geeks. I would buy the two domains though and redirect one into the other.
GeeksBlog is the one i voted for, as its more pronounceable. However, i would have GeekBlog redirecting to GeeksBlog to make sure your catching all the traffic and if people link wrongly at least they will get to your blog