If it does not go all the way through, then you should not have to worry about the crack.
As far as filling it, you have a couple of choices:
1. Caulk or silicone will work. Do not apply this if the concrete is wet - it works best on a dry surface. Be sure that the caulk is waterproof, and graded for outdoor use. If you look around at the home centers, you can probably find a type of caulk specifically for this application.
2. Hydrolic cement. This is a little more difficult to work with, but will also do a very good job of patching the crack. You may also stand a better chance of matching it to the rest of the foundation so that the crack does not stand out.
FYI, I have a few of these shallow cracks in my foundation, and have never done anything with them. So far, no problems. I usually look at them once a year or so when I am doing gardening to make sure that no more damage has occurred.