I do like to keep a stock of "hermit crab foods." However, I never buy pet store hermit crab foods, these are generally no good, some containing harmful ingredients or lot's of filler. However, a trip to the pet store can provide a lot of good treats for your hermies, such as dried fishes, bugs, seaweed and crustacean. Frozen fish food is also great, and if you can stomach it, even frozen pinky mice can be a treat for hermies.
Table scraps are the next best thing; fruit, especially tropical fruit, is loved by most hermies, edible flowers, cuts of meat and veggies, most of this is safe and good for a hermit crab to eat! You can find a complete list of safe hermit crab foods here, thanks to Julia Crab of the Epicurean Hermit. She has contributed a lot of research to provide such an extensive list. And since it's better to be aware, here's the UnSafe/Inedible Food List for hermit crabs.
That said, I'm lazy, and like to keep dry foods on stock next to the tank for when I'm in a rush and want to quickly feed them before running out the door. The Hermit Crab Addiction Store has a FANTASTIC selection of dry foods for your hermit crab, including complete food mixes and variety sample packs (which I love).
"MINE! ALL MINE!" Crabzilla hogs the food dish as everyone gathers around to sample the Epicurean Hermit's Zeaxantastic Molting Food