The default open ports are listed below but keep in mind that, any port or ports can be opened by the relay operator by configuring it in torrc or modifying the source code. The default according to src/or/policies.c (line 85 and line 1901) from the source code release release-0.4.6:

reject 0.0.0.0/8
reject 169.254.0.0/16
reject 127.0.0.0/8
reject 192.168.0.0/16
reject 10.0.0.0/8
reject 172.16.0.0/12

reject *:25
reject *:119
reject *:135-139
reject *:445
reject *:563
reject *:1214
reject *:4661-4666
reject *:6346-6429
reject *:6699
reject *:6881-6999
accept *:*