Weight training apps?

What exactly are you looking for from the app?

I'm not aware of any that work that way. In some cases, once you decide on a routine you can find apps for that particular routine... but I don't know of any that include a variety of routines for you to choose from - there are just way to many options.

Something like jefit has a ton of lifts available, sorted by muscle group... and allows you to build your own routine.

Fitocracy

I think it's best to just spend a bit of time doing some research, an app isn't going to show you proper form etc. Just google 'weight training workouts' and you will get hundreds of great pages that will give you great ideas with pics and videos of how to do them. Over the past few years I've compiled a book for myself full of different workouts and then before I go to the gym I'll write up my own session based on what I want to work on. I find it really keeps me on track once at the gym so I'm not wandering around deciding what to do.

Bodyweight - You Are Your Own Gym
Excellent app, I used it last night. It keeps time for you, shows videos before and during your work out and a lot of options to customize for target areas, time, type of workout, etc.
No equipment needed, maybe a table/chair/door once in a while. I use it when traveling or did not make it to the gym.

I found myself folding laundry during rest periods and still felt 'the good burn'.