Having three veields, you should really know this man.
No celery please, it's too hard, and even the greens are very strange things. Someone else may have more info on that, but IMO i wouldn't feed celery.
I don't have any sites to give you so here is a brief list of beneficial veggies.
Kale
Collard greens
Mustard greens
Romaine lettuce (three above are much better than this)
Carrot shavings (not too often, once every few weeks at MOST)
Grapes (green or red, seedless of course)
Strawberries (the red colour is very appetizing! don't feed these too often, high acid in them, once every week and a half at most.)
Cantaloupe (thin slices)
Mango (thin)
Oranges (not often, high acid)
That's all most people ever feed their chams, and its all you should need to. There's lots of other stuff to feed them, i couldnt think of them or didn't know about them.
Try a google search on "safe vegetables chameleons"
Or try adcham.com, good site. They may have a safe fruit/veggie list.
You can hand feed or attatch the preceding vegetables or fruits to a place close to a favourite perch. Use a paper clip, or those little black paper holding things you get at office stores. You can buy veggie clips for animals but theyre pricy and do the same things as the listed options.