OS, general software, user profile on the SSD (64GB). Games and large data (photos, music, video, torrents, etc.) are on a 2TB 5900RPM Hitachi.
Yes, temp is on the SSD, and that's exactly what I want (frequently-accessed data is exactly what you should have on the SSD). Firefox profiles are also great for the SSD. The Places database (history, bookmarks) can grow pretty large (a couple hundred MB for my main Firefox profile), and that is a huge performance bottleneck for me on HDD-based systems. Yes, putting it on a SSD means lots of writes, but it's well worth it (why shell out $ for a SSD if you don't use it?).
And you have to remember that the greatest eroder of value of a SSD over time isn't the amount of writes that you put on it: it's the fact that over time, SSDs will get bigger, faster, and cheaper and what you have now will be worth much less years from now regardless of whether you write to it or not!