I can't remember what specific brand/make/model/etc. I used in the past, but I would get one with all the little buttons or tabs around the circumference of the timer. I think most of the ones I've seen have a little button for every 1/2 hour.
I can't remember what I was doing at the time, but I would use those to be able to turn something on for a bit, off for a while, and then back on for a bit later in the day. I don't remember having any problems with them, and they seem like it's a basic enough technology that most available should work fine (sorta like a digital clock, or a radio or something).
I do remember having trouble finding timers that would accept grounded (3-prong) plugs.