There are many directories you can submit to. In fact, you are encouraged to submit to as many directories as possible (The more the merrier). However, submitting to many useless directories will not do you any good, and will be a complete waste of time. We provide a few tips here for directory submission:

Check that the directory that you submit to is:
1) Not a blacklisted FFA directory by the major search engines.
2) The page that the directory will include your site is search engine friendly. (without “?”, “&” in the URL)
3) Check that the link is search engine friendly
4) Less than 100 outgoing links on the page itself (Google Guideline for webmasters)

Here are some directories which you may consider suggesting your site to:

a) Major Directories
-Yahoo! (US$299.00 non-refundable, recurring annual fee)
-Dmoz or Google directory (It is not uncommon to wait for at least 6 months for inclusion. Whether your site can be accepted is a big question mark.)
-Microsoft bCentral ($49 annual fee)

b) Free Directories (good quality sites expected)
-Businessseek (You may expect a long queue)
-Worldsiteindex (Nicely designed web directory)
-Wowdirectory (Open for submission on certain days every week)
-Joeant (Free, provided you sign up as editor)

Some directories are strict with their submission rules. You may want to follow closely and respect the editors. Spamming them with multiple submission is a big "No No". Also, directory administrator are normally more relaxed with non profit sites (often ends with .org). If your site is adult content or sexually offensive, you may need to pay higher for submission fee. Often, directories do not include adult sites at all.

Just choose your directories and get an online submission service to do the rest. You can even ask them for their top directories and choose from within them.