I wouldn't. Focus on Google, MSN, and Yahoo. That covers over 80% of the search market. Also, there's no need to submit your site. Just get a link from a page that is already listed in these three search engines through a directory, link exchange, etc. The search engines will follow the link to your site and add it to the index.
Is it worth submitting to Looksmart + yahoo directory, too?
I haven't submitted to Looksmart in, jeez, 3 maybe 4 years? Don't bother. Yahoo is another story. It no longer passes Pagerank, but you can get some traffic. If I'm working with a big budget I submit, if it's a small one then I skip it.