View running Processes ?

Hi List !

Is there an equivalent of mysql's "SHOW PROCESSLIST" command in
PostgreS ?
Sometimes my server takes a lot of processing power, and I would
like to know what it is doing.

Also, is there no way to kill a running query from *within*
postgres ? With a query, or something similar ?
The only way I found to kill running queries was to "kill <pid>"
from a command prompt, but that is not very clean, I can't run
this from a remote client.

Thanks a lot !

Regards
--
Arnaud