Having had my own website to promote (in the same way, with little or no money to spend, so google adwords have to be kept to a minimum), here are the following tips I've picked up from other sites.
*Post about your sites in other forums, without spamming as this is considered bad etiquette.
*When posting, make sure that your signature contains a link to your wesite.
*On your emails, include a signature with a link back to your site
*Open accounts on tites such as digg and then link to your site, some users also open accounts on myspace with the same end.
*Look at offline methods of promotion such as word of mouth, leaflets (although they can cost!)
*Create a press release and use a press release website to publicise your nesw
*Look at link exchange websites as a means to promote traffic between like minded or complimentary website.

The best site I've found for hints and tips is at
http://forums.digitalpoint.com/
which has a very busy community of like minded website developers and publishers.
Hope that helps
Phil