Companion Planting and Replanting

Now that all the major players are planted in my garden, I've gone back and done some secondary planting.
I planted giant zinnias down the center of my pea beds and seeded carrots along the perimeter of the beds.  Carrots do well with peas and the bush beans that will follow the peas once that crop is finished.  The zinnias will attract some beneficial pollinators and add some color to those beds.  Zinnias make great cut flowers, but it can be hard to find those giant varieties in greenhouses.
I think that I may have finally gotten all the lily of the valley and deadly nightshade out of my new center bed.  That bed is at the top of my garden and I had high hopes for it.  The poisonous leftovers from the previous perennial bed and the early season havoc wreaked by squirrels really put a damper on my plans for that bed.  My second planting of peas ('Mr. Big') is finally coming up.  I filled in chard and lettuce seeds were there gaps.  Because of the unusually hot weather, I switched over to Cook's Garden's Summer Lettuce Mix (http://www.cooksgarden.com/vegetables/lettuce/).  I put in the last of my onion sets and seeded scallions between them.
The thermometer says "Late Summer", but here in Zone 4, we are just two weeks past last frost.  There is still time to get those plants in where they may have failed before.  Successive plantings of carrots (this is my third) guarantee that all my carrots won't be ready for picking all at once.  Best of all, planting a few lettuce seeds every few weeks means we'll have fresh salads all season long, especially with a temperature sensitive lettuce mix.