Companion planting...any done this?

Ok, so my veggie garden has been constructed, filled, watered and planned. I split it into three and have started planting some seeds/seedlings.
Put some beetroot and different lettuces in one third....got a little space for something else here.
Put carrots and onions together in half of the next third and tomatoes and marigolds in the other half. I read that marigolds help tomatoes to grow. and i planted them so they can trow a little dappled shade on the lettuce during the hottest time of the day. and the carrots and onions together as apparently the onions keep the bad bugs away from the carrot tops, which attract them. And also they grow at different depths so saves some space in the patch.
The last third is still empty. (maybe for cucumbers/some kind of bean/capsicum?)

Has anyone else used companion planting...did it work...what else can i do...i hear some herbs are good at keeping away bugs etc....tips on things that will compliment what ive already got going that i can plant in the last section????????
:D thanks

I stopped planting the marigolds with tomatoes - I swear they were attracting the snails, you could see the silver bee line straight to them.

Ooh grow capsicum! I think they are really rewarding and they come in great colours - even chocolate brown (if you go Heritage seeds or from Diggers).

The patch always looks so bare when you first start off, so I've started putting in Sweet William here and there for colour until it all grows in.

We companion plant Tomato with Basil. The basil just goes off, and the tomatoes, we got that many we had to give them away.

We have Jackie French's book on Companion planting. Worth picking up and it does not cost much.

Marigolds are good for attracting bees, but not all plants require bees for pollination. Some plants just need to be wind pollinated, I think tomatoes just need the wind.