I've been through University for a Geography degree and am now working on a PhD in Remote Sensing. As part of my undergraduate degree I did a couple of GIS courses, but they concentrated mainly on the theory and techniques of GIS rather than the practical side. We did have some practicals using ArcGIS and Idrisi, but they stayed very much in the basics.
What I'm looking for now is a good way to learn some more ArcGIS techniques to really use the power of the software. Browsing around and asking questions on this site has helped quite a bit: for example, I never realised (until I saw my supervisor do it) that you could link dataframes together, or even that you could have multiple data frames (see this question). Similarly, I suspect there are lots of ArcGIS features that could really make my life easier, but that I just don't know about. For example, I don't have the foggiest idea about geodatabases, but I suspect that they're really handy.
What I'm really looking for are tutorial recommendations, in any medium (books, videos, websites, whatever). Obviously free or cheap are better, but I do have a budget for books as part of my PhD. As I probably hinted at above, I'm more interested in general usage of ArcGIS rather than specific tools (like DEM processing or route-finding), and something that is relatively structured would be good, so that I can work through it in a sensible order.
I know this is a bit of a tall order, but any ideas?