Another good ideea is to start a web directory, with free inclusion, and with a special inclusion, something like reciprocal, but ask the submitters to add a link to your website in return for that special link (like it will show up in a premium position). 500-1000 one way links to your website can worth a lot, if not for google, for other search engines surely.
Also, build a directory, ask them if they want to join your newsletter when they submit, then send them e-mails with promotions and other goodies from all the websites you own.
It is important to have a newsletter for your website, you can even offer a discount for joining as a member (receiving newsletters) and e-mail all these precious customers and members once or twice a month with useful information and offers, only things that anyone will appreciate, otherwise they will unsubscribe.
If you sell various merchandise, don't hesitate to use stickers or even custom made scotch tape and imprinted boxes with the name of the website. As more people see the box, there' s a chance for a new visitor to your website. Throw in each box few vouchers with special products, those may reach customer's friends.
People's foreheads tattoos - as in some ebay's listings
Some cheap advertising in vouchers that are free at the cinema (multiplex type), they have information on contacting them for advertising rates. Better, print your own small advertising magazine and ask the cinema staff to leave those where people buy tickets.
Example:
I bought some movie tickets, and also took a thin magazine of a travel reservation company, while waiting in the mall for the movie to start, I choose a hotel I liked and reserved a whole week with them at the sea. They also had a big website text, of course I visited their website as soon as I reached home, and also sent the info to some friends.
Don't forget to leave few of these magazines at the dentist, people read such things while waiting
That's all I can think about right now. Hope to have more ideas.