Even with Akismet, and http:BL installed to stop spam – I still get the occasional spam comment. Until a few days ago, I simply got frustrated, went into the WordPress admin and then marked them as spam.
Then after thinking about this more, I remembered you could actually enter in your own text pattern that WordPress would use to mark comments as spam or block the comment completely. All the spam that was coming through – all had the same text in it (a series of question marks) so I added that into the “Comment BModeration” box to make sure that they were being caught appropriately – and after a week or so, I will then move that pattern down to “Comment Blacklist”. So – if you are like me and see some spam still slipping by your spam protection, take advantage of the two options to add in words, email addresses to block/send to moderation, under “Settings > Discussion”.