During the last two weeks, I've went through all blogs posts to clean up the content, reformat stuff, fix broken links and add other minor improvements. All posts have been tagged now, which should improve the "related posts" accuracy a lot and also make searching more reliable. I've also added info-boxes to various posts -- for instance, all old posts have a warning at the top, and some have a specific note attached to them.
In total, I have modified 50% of my posts (formatting mostly), tagged all of them, and re-categorized < 25%. Going forward, I'm using custom fields now and filter functions so I can make large-scale changes more easily (for instance, I've added a "project" field to all posts, so I can easily add a box which warns that a project is no longer maintained.) Finally, you'll also notice that the headings have been corrected. The twenty-ten theme I'm using has a SEO tweak which makes post titles level 2 on the front page, but level one on single-post pages. Nested headings in posts are thus broken on one of them, but there's no way to make it work everywhere without a filter. If your interested in a very simple introduction to customising WordPress, please drop me a line in the comments and I'll write about it soon.