Well, you can make your own tomato cages from hog wire or other fencing material. It's usually not too expensive and is reusable long term. Just make sure you use sturdy support stakes with it. I normally do mine on trellis type structures, since I'm using wide row, raised beds. Just easier for me to maintain.
Lettuce likes it cool, so interplant it under or around your taller plants.
Eggplant and peppers both like hot weather. Eggplant you can plant in hills like melons.
Cabbage and any of the brassicas can be planted both early spring and fall for a good crop. I normally do mine in the fall, because there are fewer bugs and I'm not as busy with other areas of the garden.
I have a few herbs, but am planning on going to containers for most of them this year as I want to be able to bring them in the house to overwinter and so I can use them for cooking. Also containers will help me control the "invasive" types.
I'd rather be gardening!