Two good choices to add to your agave collection, Kissho Kan and Blue Glow, are relatively new in the mass market, at least in Texas, but those of you in California may tell me they have been around a long time. As you can see, they make fairly large potted specimens, but those of you in warmer climates can feel safe planting them in the ground.
Kissho kan is a Japanese selection, a hybrid developed from agave potatorum, which stands out because of its variegated leaves, red spines, and interesting shape. The name is Japanese for happy crown, and you may find it listed under that name. As agaves go, it is one of the smaller ones, reaching a mature size of about one foot tall and one foot wide. I have taken a few pups from this plant, and while it takes them a while to take on the distinctive shape of the parent plant, they make really pretty little plants for dish gardens before they get too large for the dish. I have read they will take freezing temperatures down to 3 degrees F., but I take mine in for the winter.
Agave Blue Glow is a California product, a Kelly Griffin hybrid developed from agave attenuata and a. ocahuii which sports distinctive slender green leaves lined with red and yellow stripes. This plant will get larger than kissho kan, and so far I have not found any pups to pull from this plant. It is supposed to be safe in 20-25 degree F. weather, but again, I take mine in for the winter just to be sure.
I have not had either of my plants long enough to know how old they have to be before blooming and have not read if they die after blooming like traditional agaves do. But time will tell, and in the meantime, I will enjoy watching them grow.