Well, somehow some vandals managed to take control of my website and replace my content with their own. I don't know how it happened and because it took a while for me to discover the issue, my ISP wasn't much help determining the root cause.
The good news is that the WordPress database was intact, and that I had a backup of my theme files. I was able to restore (for the most part) with little difficulty. I lost a custom table in one of my posts, and I'll have to replace a few graphics files. All in all, not a terrible spot to be in. I mentioned a while back that I wanted to invest some time in automated backups of my site. Guess what I never got around to. Maybe this will motivate me.