I've started adding labels to posts, and am in the process of going back through the old posts and adding labels to those. The bad thing is that if you click on a label it will only show the last twenty posts which share that label, even if their might be hundreds.
I'll try to fix that.... but it doesn't matter so much right now anyway because most of the old posts are still unlabeled. Right now I've got something like 95 posts labeled "richmond artists", but that only goes back to 2005.
PLUS - another thing you can do is search the blog by entering your search terms in that space at the very top left... this brings up any mention of that term. So if you enter "Fiona Ross" or "Nonesuch" or "John Pollard", for example, it will bring up posts that aren't necessarily labeled. It doesn't bring up names or things that are mentioned in the comments, unfortunately.