I have a GREAT recipe and it includes all things you mentioned...
1 box Spaghetti (I use thin spaghetti)
1 bottle Italian dression (I use Ken's)
1 Package of Good Season's Zesty Italian dressing mix (the kind you buy when you are making your own dressing)
Fresh cut up tomatoes
Peppers (Red, Green, Yellow, Orange - what ever you like - I typically use at least two different kinds for color)
Cucumbers
Black olives
Feta cheese
As for the vegies & Feta, the amount is up to you. You can also double the recipe, but I would say that one recipe is quite a bit of food - especially as a side.
Just boil the pasta, strain, and rinse with cold water. Mix the dressing and dressing mix in a bowl, then put everything else in a big bowl and poor the mix over. Toss and put in the fridge. It is best if you prepare it the night before and put it in the fridge. The vegies get a better flavor. I typically toss it just before I put it out, sprinkle some extra fetta on top and some olives so that it looks pretty! :-)