Help with crunches...

Here's a link for push-up progressions, which may help with your push-up issue
http://www.5min.com/Video/How-to-do-the-Push-Up-Progression-23491574

As for crunches/sit-ups, I've never really seen a good progression that doesn't start with the basic crunch. I don't think it's cheating to wedge your feet under something, however, the biggest thing is to concentrate on using your abs and not your legs to lift yourself up.

I recently read that "it is ok to place your feet under an object to help you achieve a sit up" it did also say that you shouldn't do this if you have lower back problems (i don't know why). As a matter of fact I read it at http://www.twohundredsitups.com

Try doing the plank, it helps build your whole core. You can get some tips on doing this and more exercises at www.realsimple.com

Not sure what your ultimate goal is with the crunches??

If your goal is to work your abs, then crunches are not necessarily the best exercise to do. I agree with those folks who suggested planks to begin to build your core strength. I would recommend looking into additional exercises that work on your core strength specifically. This will not only address your abs, but also your low back muscles I(which are often neglected) and are crucial to having strong abs. You will be surprised at what exercises you can do that will work your abs - not always what you think!

Not trying to dodge the question, just trying to provide more of a solution to the actual problem, not the symptom!

Here is to your rock hard abs and strong core!!

It's not cheating, it can help your form I believe. Always watch the stress on your neck when doing situp/crunches and try to keep your hips on the ground, while using your abbs ... not hips.
Some alternatives to crunches:
- Try doing reverse crunches. Instead of "sitting up", start in an up position and gently lower down, then back up again. (you may only move a little bit here, but it will be working and lower the stress you could put on your neck).
- Lie on back, put your hands under your butt /lower back for support, then lift/lower your legs.
- Again, lie on back with bent knees, bring knees up into chest, then tap feet back to ground.
- Work the lower back too, ly on stomach and lift either/or/both hands and legs, then drop, lift again. "supermans"

For Push ups, it's one of the best exercixes around and can be changed up as you get more advanced.
Start with being on your knees for a few weeks. Then progress to being off knees if you can. Just do 3 sets with 2 minutes rests in between, and try to do as many as you can in each set. There's no shame in doing 1-1-0, just give it a go. It helps to track too, so you can see progress. It also will help to do two days on, one off.

As others have mentioned, doing planks will help. Like a push up, it will work your entire core (the muscles used to stabilize your spine).

Look into getting a fitness/swiss ball too. It's cheap and very versatile. They are good for stretching and core exercises and can increase your range of motion when doing things like crunches on them. Win Win.