I recently had ~2000 color negatives scanned by
Scan Cafe. I have a slide and negative scanner, but it is very tedious and time consuming. I have scanned quite a few images myself, but it is tedious, and I probably would not have ever finished on my own, and I don't think I could have done it as well. They now have all of my color slides (close to 2,000 more images). Their prices are going up by 5 cents per fram in a couple of days (July 14) to 29 cents for slides and 24 cents for color negatives.
There are a number of services that will do this. The reasons I went with Scan Cafe are good reviews on the quality and low price. In addition to being cheaper than most other services, they allow you to reject up to half of the images they initially scan (you can see all online and chose which to buy), and not pay for the ones you reject, while the other services make you buy every frame on each strip you send. This is nice even with slides - you don't have to take the time to sort out the good ones - just send everything and pick from the scans. Some of the complaints about them are that they send the slides and negatives to India (that's why they are so cheap) and the amount of time it takes. It is their own facility and employees in India, and you actually send your material to California where they bulk ship to India. It does take a while - my negatives took a little over 3 months.
Here is a reduced size example of a negative I scanned myself and the same frame scanned by them:
Mine:
Theirs:
Here's a full crop out of both - thiers on the left, my scan on the right: