It is going to be a personal decision; if you have extensive knowledge of imaging or scanning your criteria are likely to be different than mine.
There are many scanners on the market, including Canon if you happen to like them. A good place to start would be Apple's website but there is not much of a selection from which to choose.
They seem to be overpriced too. There are many "all in one" devices that also print and copy, and since they are less of a niche product their prices tend to be much more competitive than dedicated scanners.
These days I like Brother products. They are well supported and have a better warranty than most, and they have several "all-in-one" models for less than $100.
For recommendations, research their user reviews (Amazon for example) and disregard all that do not specifically mention the Mac or OS X. Regard any that do not have the ring of truth with a healthy degree of skepticism; same for reviews written by those with questionable literacy skills. Augment this research by going to the manufacturer's website to confirm what you learn.
Then, find the best price and buy it.