I thought I killed this one in transplant a couple of years ago, but it looks like some babies survived because it is coming back! What might its other names be? I couldn't find a match in the database.

It looks like Campanula haylodgensis to me. I'm not sure it's this cultivar, because this one might have more petals, but I'm fairly sure that this is the right species.

Bellflower (Campanula x haylodgensis 'Plena')

This one just came up in the Random Plant box. What a coincidence! It's another possibility.

Bellflower (Campanula 'Blue Angel')

I agree.
Edit:... with C. x haylodgensis, that is.

They look pretty similar, so it's hard to tell which one it might be. Might the difference between the two be in the petal count?
I got mine in a plant swap many years ago, so it has never had a label.

Thanks,

Campanula 'Blue Angel' is just another marketed cultivar of Campanula x haylodgensis 'Plena', according to the patent info:
http://www.google.com/patents/...

Thank you!