Real time query analyzer

Hi everybody!
I ask you for your help on a problem I have.
I have a postgresql 7.4 running on a dual 4 GB RAM server, but I have
some VERY memory intense queries, that put processor up to 40%. I see
all this info in unix "top" command or ps -aux
Unfortunately they don't show me the query itsself.

Is there a tool for postgres that can show me the queries and the time
they take and the amount of processor is consuming (as Oracle has) ?
I appreciate any help.

Thank you,

Adrian