KGS, the Kiseido Go Server, has software in the client and server especially for reviewing and teaching.
Sorted by professional rank (if known) and KGS rank. These can be more or less active. List has been reviewed on 2004-11-19, expired accounts have been purged.
(Name displays "[9d?]", rank graph displays 10d.)
For more information about fees and availability see their User Information profiles on KGS.
To compare ranks, see Rank - worldwide comparison or its formatted version.
Other teachers may teach for free.