Do you find that you get traffic from lots of little search engines? They may not add to a huge number but I never use to see this before. However, recently, I find I get quite a few from all sorts of search engines that I didn't realise actually existed. Some are big btrands like the BBC and CNN (both of which recently started their own search engines, perhaps powered by one of the bigger search engines, I don't know). Also, there are other names that I've never come across.
I only got traffic from google, yahoo, msn and aol, never from small search engines. But I saw many small or unknow spiders crawl my website regularly.
I keep downloading my sites to a lot of search engines using addweb... I get a lot of links from others... You need to do this frequently say once a week.