Okay, here's one of my favorite meals for you: Stuffed peppers.
Cut the top of a red pepper, and hollow out the inside. Fill the inside with couscous and little chunks of cheese (Cheddar works, but Mozzarella is better), go easy on the cheese though, as it's the most unhealthy part. Don't fill it all the way to the, leave about half an inch empty.
Put the top of the pepper back on like a lid, then bake in the oven at 180°C until the pepper is nicely roasted (It won't take long, maybe around 10mins). While it's in the oven, quickly make yourself up a nice side salad (Go easy on the dressing, need to keep this healthy). then when it's done, take off the "lid" and cover the top of the filling with a layer of hummus. Put the lid back on and enjoy... best enjoyed with a glass of white whine : )
As for things to snack on, most of the obvious one's have already been said. But I do have a couple of additions for you. Sweetcorn is great, it fills you up, but so long as you swallow it whole, your body can't break it down, and it will come straight out the other end undigested. Tasty food, and no calories (Although it is kinda gross if you think about it too much)
Grapes have already been mentioned, but what's been missed is freezing them, it sounds crazy, but try it. Freeze them overnight, then get them out around 10 mins before you want some to let them thaw a little. They get kinda crunchy and cold, and some how this only makes them more tasty, especially on a warm summer day.
Coffee works great as an appetite suppressant, so drinking plenty of that can help keep things under control as well.
Finally, once a week have one meal where you eat whatever you like without worrying about it. If you try to stick to a really rigid diet, it' easy to under up getting a bit depressed about it, especially if your missing all the old no-healthy foods. By having one quilt free meal a week, it means you're less lightly to slip up (Cos you have something to look forward to) and it means you won't end up missing it so much that you end up going on a massive binge.
Good luck with your continued health eating : )