On the same machine for which I created the Wiki, .odbc.ini is in ~ or /home/<your login> if you prefer.
Thanks for asking. 
I will take some time to review and probably enhance the wiki in the next few hours, so you might see some updates there and/or an edit here.
EDIT
Oops, I gave an answer for .odbc.ini and not odbc.ini, (The first starts with a period and is a different file). (ref)
odbc.ini - /etc/odbc.ini
.odbc.ini - /home/eric/.odbc.ini