I use a variety of things for Finn, including: boiled chicken, hot dogs, salami (microwaved so not so slimy), string cheese, freeze dried liver (big tub from Stewarts), and other freeze dried treats (mostly Orijen). If training at home with limited distractions, I just use kibble.
I used the boiled chicken and hot dogs the most, they are the cheapest and upset his stomach the least. I just prepare large batches, store them in the snacksized ziplocks, and freeze them. Finn will eat them frozen or thawed.