I've set things so comments have to come from some registered ID: OpenID, Blogger, or whatever else Blogger will take. This cuts down spam somewhat. But I delete comments that look like spam. I've been seeing more of these lately, things like "Great post on X, for more on X see (website)". I just delete them. If I've deleted one of yours in error, feel free to try again, but make the comment look less spammy and perhaps wonder why you've failed a Turing test.