Another tool for this job is RANCID, which actually takes Pancho several steps further and provides configuration change management when coupled with CVS or Subversion. It can even perform e-mail notifications when changes are made to device configurations, which can help immeasurably when trying to figure out why an entire wing of the building suddenly fell off the network. Implementing RANCID is more involved than Pancho, but it also does much more than Pancho. Either way, implementing a configuration backup plan like this should be mandatory for a network of any size.
As far as the other little pieces, like firmware updates, BIOS images, and whatnot, they need a home. I'm guilty of this one myself -- downloading firmware updates for a blade chassis, say, and then leaving the files on the desktop of whatever system I was using to perform the update. I then promptly forget about them, or even remove the system altogether if it was a VM. In the face of a failure or a need to reapply the firmware, the time saved by not having to relocate and redownload the right image can be extremely valuable. As we all know, navigating hardware vendor's sites looking for that one image file can be a chore. Also, trying to decipher the filename of the image can also be a chore, so keep a text-file list in the directory detailing what is what. Even better, add it to the IT wiki (you do have an IT Wiki, right?).
All this could be summed up with a simple "be prepared," but I've found that reminders like these lead to smiles after a catastrophe is averted rather than madness when it isn't. You can thank me later.