I'm pretty much with DogFish on this; I also think you might have a bit more time then you realize. - The undergravel will continue to handle it's share of the filtration, as will any plants you may have. Diana's got a great suggestion with hanging the filterbag/sponge/whatever in front of the powerhead outlets.
Remember, people fairly regularly ship fish in bags of water that don't get changed for a good day or two. Your fish in the tank have a much better fish:water ratio, and it is getting filtered (just not as much).
What did you check/clean on the HOB? Were you able to get the impeller out and look at it? clean out that area?
Is it completely dead, or is it making noises when you plug it in, but not moving water? Have you tried plugging it into a different outlet?
Not trying to ask dumb questions or come across as insulting or anything, just looking for anything that might indicate that there is some other option outside of buying a new filter.
If nothing else, try and do an ammonia (and maybe nitrite) test when you get up, if they come up 0, you can probably let it go till the afternoon, if not, maybe do a partial water change, and deal with it in the afternoon - just don't add any more food until you get this filtration mess sorted out.
Maybe add one of the products that neutralizes ammonia/nitrites if you have any on-hand.
Last edited by lochaber; 11-10-2013 at 05:31 AM.