Workout Advice Please?????????

Okay, so, I'm in Kansas for the summer, and I need some good advice on how to work out. I have no weights or anything, I've been doing pushups and situps, but I just want to know some good workout plans that are effective, I've been doings pushups throughout the day, not really a workout, but 30 every 2 hours. Im wondering if this is effective, also, on some days, I'll just do 5 sets of pushups until I fail all at once, then not workout. Also, some excercises would be gladly appreciated, I'm only planning to work on my arms, since my abs are already where I want them. Thank you.