Patching Material For Concrete Suggestions ?

Hello:

Have some foundation cracks, and also a few cracks in a garrage concrete floor.

Would like to fill them and repair them if possible, and hope there's no additional settling which I imagine no filler type of repair would withstand, no matter how minor the movement.

Was wondering:

a. Do I want an absolutely rigid, or semi-flexible patching material ?

b. What's the "state of the art" these days for these types of repair materials ? Epoxy based, or... ?

Any specific brands recommendations, caveats on their usages, etc. would be most appreciated.

(would like it to be waterproof, also)

Thanks, Bob