I'm always on the look out for blogs by other people working in special libraries, and particularly museum libraries, so the first thing I did was have a scan through to see if I could find any. As usual there weren't that many, but perhaps as the course goes on more will feel inclined to take part.
As I'm organising a CPD23 meet up in Cardiff I also went through looking for any participants in my area. I've already started to put together a list using Delicious to find any tagged with Wales, which will hopefully grow as people start setting up their blogs.
However the best ways I've found to keep up to date with who is taking part in CPD23 is to subscribe to the CPD23 single feed on their website, and to save the #cpd23 hashtag as a column in TweetDeck on my phone.