We've used the Zuke's mini naturals too and I like them. I've also used cheese and something that's a super cheap soft treat is hot dogs. You can usually get a package of chicken wieners for about $1-$1.50 and slice them up into little bite-sized pieces. I don't normally feed treats like that now, but when I was doing agility lessons with Lightning I used the hot dogs.
Beware of Mushers...They will suck you into their addiction!
If your dog thinks you're the best, don't seek a second opinion!