query result set caching

Dear All:

Im looking for solutions (Free Software is better) to do query result
caching.
Thanks to the people from #postgresql I know that postgres doesn't do
that by himself and the solution should be some kind of middle ware.

This is our problem: we are executing the same set of SELECT SP/queries
hundreds of times, without updating the DB. We would like to cache the
result of this SP/queries so the next time somebody runs one of them,
the results come from the cache instead of the db.

We would like to use an already developed and tested solution but if we
can't find anything that fits our needs, we can develop our own solution
(playing w/ PHP and PG's LISTEN/NOTIFY)

Thanks in advance