I have met a huge number of people lately who cannot seem to be able to tell what they Personal Best is at any particular distance. It's not that they don't care about it - it's that they have never bothered to track it. The thing is, though, that they really seem to care about whether or not their times are improving at the various race distances.
A while back - I discovered a tool to help with just that problem. Athlinks.
Athlinks is a website where you can search for your name and it will pull up all of the races that has someone of that name running them. If you set up a free profile, you can then "claim" the races that were actually yours - allowing you to see your improvements over time. You can also search for your races under a maiden name and add those to your profile as well.
It also gives you the ability to comment on certain races (like last year when my Big Run 10k end up being a ridiculous 14k long, yet my time looks like I had an 1:40 10K)
It only pulled chip timed races so those super speedy fun runs won't show up in the listings...but it can give you a pretty good idea of what your PB might have been for any particular distance.
Athlinks also has a social component to it - You can add friends and rivals. I don't tend to use it for that. I don't really tend to use it at all, but for someone who would like to take a snapshot of where their race times have been...it's fun to play around with.