As a video production professional who has worked powerpoint/awards ceremonies for major corporations, I think things went fairly well. Considering the fact that this was a no-budget, volunteer, primarily 1-person operation, I think you did an exemplary job.
There were only a couple gaffes, and unfortunately they all came close together which caused a little confusion for a moment. As others have mentioned, the occasional gaffe is to be expected in a live show. You don't have to like it, but accept it and move on.
I'm not sure having the companies make their own slides will necessarily fly. They may not have the time or resources to do so, and you lose control over file size, etc. You might consider having one of the various artistic folks here create teh slides based on your specifications, and then you'd olnly have to compile them - this works best if you can get it all done well ahead of time.
Suggestion for future shows:
1) Try to get the main presenter there to run through the slides the day before-hand. Or at least have some one go through the list of nominees with you as you page through the slides. Extra eyeballs will help catch things like the wrong cover for the one product. Doing it a day before-hand will allow you time to fix things.
2) Have backup lists of nominees so that if someone misplaces theirs (like Mike did) there's an extra at the podium, as well as at the powerpoint PC.
3) Use the Powerpoint presentation printout to help keep track of things - this also acts as yet another backup on point 2).