I have not only seen cat3 in the wild, I still know of a dorm that is pre-cat3, uncategorized phone cable. It is a very loosely twisted air cable, and it is punched through standard 66 blocks, sharing cables with analog voice. Sometimes to get a room the 2 pair needed a single pair is stolen from 2 other rooms.
And for you cable monkeys out there, there are spots in that building with cables carrying ethernet on cables spliced with UYs
Yep, it does work, and will even connect at 100M most of the time.
It is the last dorm on campus that isn't at least Cat5e, with several that are Cat6a now. It is becoming less of a problem, since almost all students are coming equipped with laptops, and 802.11n wireless is much more convenient. There are probably a few runs in that building still nailed down at 10half, because those runs were flaky enough that the NIC would negotiate to 100M and then error 99 percent of the packets.