[Techtalk] Performance Monitoring, Linux

[sara]

Hi all, 

I was wondering what are the best utilities (GUI and otherwise)
available for Linux for monitoring the performance of hardware (CPU,
memory, hard drive, etc.)? 

Ideal would be something that allows a real-time (albeit inaccurate)
view with visual feedback in the form of a graph of some sort, AND
performance logging-over time, like the Windows performance monitor. 

I know several minutes of research should turn up an amazing number of
tools for doing this, but I just thought I'd ask you guys first to see
what people are using in real life. =] 

Thanks in advance!


-Sara