I've been a big user of .Mac Galleries w/iPhoto for years, and will miss it for its convenience (especially for other family members)
I'm thinking of
Smugmug as a replacement.
even though it's not free (but still cheaper than .Mac), I really like the high quality look to the galleries, the professional looking layout/templates, and the ability to manage privacy settings on an individual per-gallery basis - something I used in .Mac Galleries too. there seems to be some plugin the let you easily upload iPhoto albums to smugmug.
I've used Flickr for some misc stuff, but my main (large!) photo collection is not there. I realize there are some ways to control private photos in Flickr, but overall I just don't like how Flickr displays photos (somehow, it feels like the photos take a backseat to all the other stuff on the pages in Flickr, IMO).
the one feature of Galleries that it seems to be missing in Smugmug for me is the ability for friends or family members to upload photos directly to my galleries & iPhoto library (e.g. photos of some event we all attended), although they can email photos to a special address to do so.