If they’re “real people” as opposed to bots, there’s not much you can do beyond the moderating you’re already using….
Moderator
James Huff
(@macmanx)
Volunteer Moderator
If the comments all have common themes, then they’re probably bots and can be blocked with your moderation list or blacklist. Other solutions can be found here: http://codex.wordpress.org/Combating_Comment_Spam
If these are legitimate human beings advertising legitimate personal blogs, then there is little you can do to stop them short of simply deleting their comments after the fact.
They’re real people. They’re just annoying people who don’t deserve to be taking up my time :p
Moderator
James Huff
(@macmanx)
Volunteer Moderator
If they have a common username, email, URL, or IP just add it to your moderation list. Personally, I’d recommend going a step further and add their URL to your Comment Blacklist. You’ll never see their site-promoting comments again. More info: http://codex.wordpress.org/Combating_Comment_Spam#Comment_Blacklist
I haven’t actually used one of the nukers or whatever since 1.5, because I’ve found moderation to be working well enough for me. But I may have to implement it again one day. Silly spammers making life difficult.