I know I'm gonna get beat up for this, but worrying about keyword density is the wrong thing to focus on.
I check my stats periodically and see what natural keyphrases are being searched repeatedly and just blog using those as topics. Great way to get blogposts and to nail your keyphrases in a more natural way. Another thing I do using that keyphrase list in my stats is to keep it in mind while I blog, and after writing any article I'll simply look through and compare what I wrote to my keyphrase list. Then I'll change a few things based on that-- like "site design" to "website design". I never worry much about frequency. I just write naturally, and then tweak just a bit. It's worked well for me. Google says to write for your visitors. That's what I do (with just a BIT of
SEO tweak to help things along!)