pcihpview is a GTK+ program that displays all PCI Hotplug slots in the system and allows you to enable and disable slots, and change the attention light values.

pcihpview uses GTK+ 1.2 and requires that you have a PCI Hotplug controller driver loaded in your system, and the pcihpfs filesystem mounted.

Here is the obligitory screenshot:
pcihpview screenshot

The changelog for pcihpview can be viewed here.
Source for pcihpview-0.5
Binary RPM for pcihpview-0.5
Source RPM for pcihpview-0.5

BitKeeper tree
The BitKeeper tree for pcihpview can be browsed here.

Linux driver for the Compaq Hotplug PCI controller
The PCI Hotplug Driver for the Compaq Hotplug PCI controller is now in the mainline kernel tree as of 2.4.15-pre4, so no patches are necessary.

For those who want to see the history of the driver over time, here are the older patches:
Patch against 2.4.13-pre5
Patch against 2.4.13-pre1
Patch against 2.4.11-pre5
Patch against 2.4.10
Patch against 2.4.10-pre12
Patch against 2.4.10-pre10
Patch against 2.4.10-pre8
Patch against 2.4.9
Patch against 2.4.9-ac6
Patch against 2.4.10-pre4
Patch against 2.4.8-ac8
Patch against 2.4.8-ac2
Patch against 2.4.8-pre3
Patch against 2.4.7-ac5
Patch against 2.4.7
Patch against 2.4.7-pre6
Patch against 2.4.6
Patch against 2.4.5-ac24
Patch against 2.4.6-pre1
Patch against 2.4.4

Please see the Compaq PCI Hot Plug for Linux project page for more information on this driver and for links to userspace tools for the older kernel driver versions.