There are means of 'disguising' recipient addresses by trying to trick
the email client, but the problem with that is that it will only work
on certain email clients and the bigger issue is that doing so would
cause a great many spam filters to detect your email as spam, and in
certain cases a mail server could reject it altogether. So it's just
a bad idea all the way around.
BCC is a working solution for most casual users, and for the rest
sending individual copies of each email to each recipient is the
solution. I can't imagine there will be an answer that doesn't
involve one of those two options but if you care to explain exactly
what you're trying to accomplish we could examine it from that
perspective.
-matt