Lots of broken spokes on one bike, with different wheels I have a commuting bike I've had for a few years, and as long as I've had it it's frequently broken spokes on the front wheel. Eventually I got sick of replacing them, put it down to a bad wheel, and replaced it with another wheel I had lying around. This second wheel is a decent Mavic touring rim on a Shimano Deore hub, and it's done a couple of years of trouble free service on a previous bike.
Anyway, within a couple of months I got my first broken spoke and now it's the same pattern as before. Each time I replace I true the wheel up carefully and then check it again after a couple of days.

Over the last 20 odd years on several bikes I remember very few broken spokes- once on a loaded tourer, and maybe one or two MTBing.

So my question is this: Is there anything about a particular bike that might cause a lot of broken spokes- maybe forks slightly out of true or something? 
It's a single speed with a reasonably high gear (45x16) and I am frequently out of the saddle but I can't think this would be any more or an issue than climbing hills on my road bike.

UPDATE

So a month or so ago I broke 3 spokes in 3 rides, and ran out of patience. After letting the bike sit in a corner for a bit I found a cheap replacement fork and swapped it over. A couple of weeks later and everything is good, so at the moment it looks like that was the problem- early days yet though I suppose, as it took a while for the original setup to start popping spokes and now the wheel might have a few dodgy ones in it.

Thanks for all the suggestions!
Are your brakes properly aligned? If they're off-center, every time you brake you'll generate a lateral force on the wheel that spokes absolutely hate.
How do you store your bicycles? Do they live in the garage or in the living room? If you live near the beach, the salt can cause corrosion and weaken the components.
Like the comments said, check the fork alignment. Since you stated that you had a wheel lying around that had never been a problem before mounting it on this particular bike, it leads me to think that there is something wrong with the current bike.