Here is a load of Tenhou game logs (by which I mean actual gameplay logs in Tenhou's format, not just results). There is not much now, but (very soon) I intend to add more data on the logs so you can search through them and stuff. I also intend to add more logs in general. Until then, see f/, list.txt, list.html for a plain directory listing. Perl scripts and such coming soon!
You are free, and invited to, rip all the logs from the f/ directory as you wish (just feed the page into wget).