Listing devices in Linux

I'm looking for RedHat command specifically. I know ioscan in HPUX, and dmesg will show all devices at boot on Solaris, but I can't think of the Linux command.

Looking for a record response time from some of you on this one.

dmesg works on Linux, too. And in KDE they list the devices in the control panel thingy.

Yah, dmesg, gives you the boot and driver messages. But do you know about the proc file system? Everything about everyone is in there. It's mounted as /proc, so /proc/cpuinfo describes your cpu, /proc/pci covers the pci bus, etc.