If for example you have a site on mp3s you can google "MP3 add url" my preferred option though is to use yahoo site explorer. enter the url of the competition and see which sites are linking to them. Also al ot of blogs have decent pr
now so see if you can stick a link on them. Try to make your post relevant though if you want it to remain.
Also have a blog of your own.
Another thing is have a profile on the social networks. You can stick your sites in your profile and also post links into relevant groups.
Stick social bookmarks on your sites too so people can bookmark your site in spurl etc... Although they will only do that if your site is any good.