Has anyone bred from an older dog?  I am considering breeding from my just turned 7 year old.  She has had one litter and is fit and healthy, but I am obviously concerned.

Not ideal, but it would depend on the breed. Some large breeds are geriatric at 7, some are still 'young' at 7.
Also, how is her general health?

I know this might sound stupidly basic advice but have you checked with the K.C. that you can breed her at this age I am not sure what the upper age limit is and the rules around it are

I personally, would never breed from a bitch at 7.  She doesn't deserve it.

It depends on the breed. Some are in their prime at 7 years old, while other breeds are well past it. I wouldn't consider a first litter from one that age, but if she'd whelped a healthy litter before she was 5 nd was in tip-top condition I'd certainly consider it, especially if she's of a vulnerable breed which needs all the litters they can get.

Mine were retired and spayed by 7.   If you've had a litter from her already, why put her through that again even if doing so would be better than had she not had a litter before?   Every time a bitch is mated and in whelp, she is quite literally at risk should it all go pear-shaped.    Of course it depends on the individual animal, her health and I have to say, what she has to contribute to her breed still.  

If you want my honest opinion, don't do it.   Leave it to the younger bitches!

Absolutely depends on the breed. A 7 year old in my main breed would be in its prime still and I'd not think twice.

If breeding for the right reasons i.e. to keep a pup, she is fit and healthy, coped well with her previous litter etc - I personally would

I agree, if she's fit and well and has had a litter before, I don't see any reason why not.

Even the 'not past 8 years old' thing is a result of the UK KC's ruling on not registering pups from bitches over that age.  The AKC will register pups born to bitches at any age and breeders in the US (even responsible and reputable breeders) think nothing of breeding from a bitch older than 8yo...

You might have a smaller than usual litter, as fertility does decrease in older bitches.

Both the two bitches I've bred from (small breed) were 6 years old when they had their second litters, partly because it took a few attempts to get them in whelp the first time, and they had no trouble. Depending on the breed and general fitness of your girl you should be fine.