+1 on the Spyderco Sharpmaker.
Keep in mind that both the Sharpmaker and the clamp type systems systems will slightly round off the tips of the serrations. This is a result of the serrations being ground down slightly since you are not using stones formed to grind serrations like the manufacturer did. IMHO (and the way I do it), the way to reduce this is to do most of your sharpening on the side of the blade that the serrations are ground on, taking as little metal off the unground side as possible. Note this is the opposite of what is suggested above, but I must admit i have not tried rcmodel's method yet. I will have to try that, and perhaps change my methods.
Ok back to theory that I have read, and prototyped in my mind to verify, but not had the budget to try yet:
If you really want to keep the tips sharp, or fix some abused/broken serrations, you need to get some slipstones that are the same shape as your serrations (if you have to you can reshape japanese waterstone slipstones to fit). These are normally used to sharpen small woodcarving gouges. Alternately you could get some tool and die maker round stone files.
Lansky sells some "Dogbone" Sharpeners that are shaped to fit the Spyderco and Cold steel serration patterns, but I keep forgetting to buy one.
As for a breadknife:
(a taskNot for the impatient/lazy)
You can rework/resharpen it with a chainsaw file if it is soft (What I did since it was a softer thrift store rescue knife), but if it is harder you could use a dremel or the above mentioned stones of diameter appropriate to the serration size. This may take some trial and error to find the right diameter file, however.
First you need to join the teeth just like when sharpening a handsaw. Use regular files or stones to do this. Then individually regrind each serration, maintaining the original geometry if you like, or changing it to better suit your needs and wishes. Finish off each serration with abrasive string or a leather thong impregnated with Chromium Oxide compound.
I wish i had a camera so could show you how wicked my breadknife looks. It has a serrations going along the belly that is near the tip, which lets you gut all the way through without hanging the end of the handle blade off the cutting board.