Like applestar pointed out, they can be thinned pretty easily as they are able to stand a good bit of handling if done gently. I have also found that salad green seedlings in lettuces, kale, chard, etc. can be thinned aggressively since they do transplant well with a surprisingly high survival rate if kept watered until their roots take hold in their new spot.
I've got all my salad greens except black seeded simpson and spinach up and growing right now. I think those seeds were too old to use but I tried them anyway, but have since gotten new packets to put in this Saturday.
I do have a good crop of pole beans coming in and picked a gallon container full of them yesterday with the vines loaded with smaller ones and tons of flowers. I also am picking pickling and slicing cucumbers and got 8 off the vines yesterday, along with a nice container of habanero peppers. My tomato plants are thriving now and there are several small tomatoes on them, so if we don't get any frost until December, I should be able to pick a good bunch by Thanksgiving and beyond.
Love gardening this time of year.