find open transactions/locks in 7.2?

[select version() --> PostgreSQL 7.2 on i686-pc-linux-gnu, compiled by GCC 3.0.4]

I'm getting hangups every day or so, I presume due to some open transaction
that insert/update/delete'ed on a table that is used by my main app without
a commit.

Is there some way (in 7.2!) to find who's locking what or who has
a transaction open? 

-- George

-- I cannot think why the whole bed of the ocean isnot one solid mass of oysters, so prolific they seem. Ah,I am
wandering!Strange how the brain controls the brain!-- Sherlock Holmes in "The Dying Detective"