Personally, I think there is little value in submitting your site to search engines these days - it's just as well to get listed organically. While there are things I do to help search engines along (semantic markup, ensuring URLs are friendly and that pages have a single URL), there are so many factors involved these days, that I don't see too much point in trying too hard - unless SEO is your business, or in your business' interest.
Lorna, thanks for this post - a good reminder that I actually need to post something for bots to pick up on! Fresh content will keep your search rankings fresh.
By the way, I use Brian Warren's anti-spam plugin for textpattern because CAPTCHA's are inherently inaccessible. Even a confirm checkbox or an extra field in your comment form asking an answer to a simple question would be a more accessible solution.