You know, vegetarians eat a lot of stuff that isn't vegetables!
I would probably follow Cathe's idea and also make some stuff that you like with meat, but a veggie version. I would make a list of your top 20 favorite meals and then look to see how you could alter them to make them veggie without changing them too much. You can also see where it's possible to add veggies to them. So if you're having spaghetti with meat sauce you can have spaghetti with marinara and something like Yves' Ground Round fake meat and sautee some chopped up veggies with lots of onions and garlic to add to the sauce in small pieces.
I really like making lentil and rice pilaf - it's a one-dish meal, and you can add whichever veggies you want to it. We have onions, garlic, carrots, sometimes celery, green beans, etc.
Seitan makes a wonderful meat substitute and it's easy to cook. We use whitewaves' Chicken-style and break it into pieces and cook on md-high heat with olive oil, garlic, and red peppers. It's just like chicken nd you can serve it with a variety of grains, pastas, and veggies.
We also make lots of tacos, burritos, and taco bowls - beans, rice, avocado, salsa, onion, sour cream, cheese, and if you want, some of the seitan but in smaller pieces cooked with cumin and some cayenne.
Some great cookbooks:
The vegetarian meat and potatoes cookbook
Personally, I prefer to stick with specific regions/countries and make veggie versions of that food rather than the more general veggie cookbooks.
Going out to eat:
Mexican/other Central American countries