what is the best free webhosting and domain name for a game for unity3d?
Wordpress or Blogger can get a site up and running fastest in my opinion.
Why don’t you simply get a cheap paid hosting company? Google it and you’ll find dozens. It’s the best way.
I use http://www.000webhost.com/ the free options vary a little script wise if you choose your base as windows vs linux. Like .Net vs. java, perl yada yada. But as for free goes it offers much. Like both give you php with 5 sql dbs. I also like having the 5 free webmail / imap accounts. There isn’t all that much free space being offered (1.5GB) but the 100GB bandwidth is nice to have. Heck I can do plenty with 1.5Gb. 
Free domain you want? Not happening. The closest thing to that is co.cc
to share and show unity3d webplayers and simple html pages, you can use dropbox, i use it for my tiny lame site haahaha and to showcase some unity webplayers experiments to friends, you can get a dropbox account and if you dont want the url you can use dot.tk to get a free .tk domain to use in companion with your dropbox account
you can get a free dropbox account here:
you can get a free .tk domain here:
also you can take a look at my simple and lame website here, completely hosted in dropbox if you want to try out how a .tk domain redirect would work
you can make a masking redirection if you have an actual purchased domain too as you can see here (same dropbox hosted website)
hope it helps