Update regularly.
Keep navigation good and content easy to find.
Sites that are fast to load keep visitors visiting.
Put your site up for awards, but try to avoid "automatic award Submiters" because they don't work.
Send friendly emails to "Internet magazines" and ask for a listing in their top 10 sections etc.
Tell visitors how to bookmark your site. Remember some surfers are not very experienced with the Internet and repeat visitors are the best form of traffic you can have.
Be unique. Add the things that your competitors wouldn't think of adding.
If you have time, follow up every email you receive. That way people start to remember you.
Add a hyperlink to email signatures. Some people add a little slogan.
Contact "technology/computing" sections of newspapers and ask kindly for a listing.
An occasional competition can draw extra traffic.
Submit to the Open Directory for better link relevancy, particularly on Google. http://www.dmoz.org/
Utilise search engines as they are an ideal form of FREE traffic.
Make sure your pages are search-engine friendly, visit
http://www.selfpromotion.com and http://www.searchengineforums.com/ to read the spiel.
A trial copy (30 days) of WebPosition Gold (http://www.webposition.com) will help to improve keyword density and other factors that greatly influence search engine rankings.
Once you have enough regular visitors, the odd advert is ideal for some extra cash. Make sure they aren't obtrusive though.
Don't pay for promotion. The best and most effective ways to increase traffic do not require a wallet!