Picasa Web Albums can do this but there is no security to keep
others from crusing thru your other collections (not good)
There are many picture hosting websites that allow security for
each directory (Album/gig) but they are not free. I hear Smugmug is
one of the cleanest and most reliable.
Actually, with Picasa Web Albums you can set the security on
your albums to only people with a link. This will only allow people
with the link to see the album. It does not make your album public.
However, anyone with the link can see the entire album. It's a
little tricky to set up, now that Google is trying to push Google+
and photos, but it's there if play with it. You can disable the
link at anytime. I can give more details if anyone is
With Picasa web albums your guests can download the entire album
with a few clicks if they have Picasa on their PC.