I like the doggos because I have one myself. Too bad there aren't any border collies (well except that mixed one).
I added a link to the LOGO! PLC from siemens. They are excellent, and are the best PLC for people that are new to PLC's. Their possibilities are endless. Also, the newest version (the OBA8) has a web interface and can be controlled over WAN, so maybe that is interesting hacking material?
I also included a book to learn how to program a LOGO!