Every day I usually find 1 new site that links to mine by looking through my logs. I submit each URL to Google. Why do I do this? Well Google ranks pages based on links pointing to them, and if Google doesn't know about the link then it doesn't help me any.
So make sure that you not only submit your site, but also submit the sites of those linking to you. I personally get alot of teachers linking to me from their online syllabi, such pages would never be found unless I submitted them.