I'm trying to remember what sets were available with the online game. I think Hammer of Thor was the initial one, but were there others? Weren't there ones that were original characters?

Go to Units Advanced Search, and for "Environment" select "HeroClix Online." That'll show you the Marvel and DC pieces.

There was also a "Starter Set" with original characters, described in this thread:

http://www.hcrealms.com/forum/showthread.php?t=474845

-J

What RavenProject said.

The original characters were interesting additions that I wish they'd (1) port into "real Clix" or (2) port into "real Clix" and develop more of!