The added advantage to submitting multiple pages is that it will improve your site’s “popularity” rating, because the pages you submit will usually have links to other pages on your site. Not all search engines will count internal links, but some of them appear to do so. Although submitting multiple pages does take time, it’s generally worthwhile to submit at least the entry pages to key sections. Submitting all pages is probably a waste of time, since your most relevant pages (which will appear higher in the rankings) are going to be the entry pages anyway.
Keep in mind that this advice applies to search engines only! If you submit 100 pages to Yahoo! or Open Directory, you’ll probably find that they never list your site. For directories that are indexed by human beings, treat them like human beings, and don’t make their job difficult.
If you decide that search engine submission is important to your site’s success, then you should seriously consider using software to automate the submission process . Many search engines will drop your site from their index after a while, and you will need to submit your pages all over again. The more pages you submit, the longer it takes to submit them by hand.