Seomoz has lots of great information. I subscribe to their blog posts to make sure that I keep up to date on the latest findings and developments across the seo world.
but SEO takes a lot of time, and its easy to forget things.
I try to spend a couple of hours a week tidying up my site, whether its changing the theme, fixing some poorly performing code or just making sure that older posts still have relevant uptodate information in them.
I have 600 posts at this point, not a lot (I deal with sites at work that have close to 500k pages each) but still enough to eat away a lot of my free time.
this list is an excellent checklist of things that you can do when you have a spare hour to check over your site to make sure that it will perform at its best.
there are beginners techniques all the way to advanced things, but there will certainly be something that you can do :)