Like Bleep said, in order to speed it up more than a little, you need to cool it down too. the ramsinks are almost a necessity if you increase your memory speed a lot.
RADCLOCKER is a nice and easy application to overclock your Radeon.
do a google search and you'll find it easily enough.
If you read some reviews such as the one found on ANANDTECH, you'll see that these cards can easily be overclocked without the extra cooling to a certain limit, but overclocking does reduce the life of your card drastically if you don't cool it down.
My gaming machine:
P4 2.8 GHz
2 X 512 MHz PC3200 in dual DDR mode
Intel D865PERL MOBO
integrated 6.1 MAX audio
Logitech duo MX mouse and KB
ATI RADEON 9800 PRO