is there SCVMM Lite? or System Center Virtual Machine Manager for non-enterprises?

Not as such, but  System Center Essentials 2010 has some virtualization management features that come from it.

With Office 365, can I use my own domain name?

yes.  http://onlinehelp.microsoft.com/en-us/office365-enterprises/ff637595.aspx

What does Office 365 cost?

for individuals and small businesses it starts at $6 per month per user.

more information here: http://office365.microsoft.com/

also the fact sheet has detailed pricing.

http://office365.microsoft.com/uploadedfiles/office365factsheet.docx