I have been going to the gym a lot lately and I have been using three iphone apps that I absolutely love. They are also the only apps I have ever paid for, the other ones I have are all free.
My bitch/sister introduced me to a website, hundredpushups.com, that gives you a pushup program based on how many you can do after an "initial test". They also have an iphone app. You do five sets of pushups three days a week, and they just increase the amount that you need to do each time. I started being able to do six pushups (with my knees on the ground!) and when I did my sets on Saturday, the five sets totaled 130 pushups. It's so cool. I am superman.
My friend Diana introduced me to another app that is called Couchto10k. You start the program not being able to run very far at all, and at the end you can run a 10k. You listen to music on your phone and it interrupts and tells you when to walk and when to run. The first week you are walking for 4.5 minutes and running for 30 seconds, and then the second week the walking decreases to 4 minutes and the running increases to 1 minute, and then more the following week. You do it 3 times a week as well. I am not that far into it yet but so far I really enjoy it. It's like a game.
I also got iFitness on my phone because when I was working out at the gym I would always forget how many reps I had done and how much weight I had done the previous time. With iFitness you punch in the weight and repetitions, as well as any cardio that you do. There are lots of cool features like a weight tracker, BMI calculator, and TONS of exercises with videos and descriptions of what you should do and why you should do it. You can create routines for yourself that are like little playlists with all the exercises that you want to do in that routine. I have a "pushup days" list with pushups (the hundredpushups ones) and abs and legs stuff. Then on "running days" my list has running and more arms, chest, and back stuff. It's really cool to have because I never forget what to do each day and it makes it really structured.
All of these apps are great and I think they make me much more motivated and "on track" to workout. Enjoy!