As I'm doing more and more photo shoots, I'm looking for a site in which I can post proofs for clients to look at. I would use Flickr, however the images can be downloaded and I obviously don't want proofs to be downloaded before they have been edited. Can anyone recommend a site that I can use?
SmugMug.com for sure. Tons of security features both to protect the photographer's work (right click protection, watermarking, image size limitations) and to protect privacy (password protected galleries, password protected sites, unlisted galleries). Not to mention all the commerce features and other Pro oriented stuffs.
NOTE: I am a SmugMug employee :D
Along with SmugMug, Zenfolio and PhotoShelter also has the same features, so compare them and find one that suits your needs.
Many options exist for this, and over time these company's seem to come and go but I'll note some of the recent ones that I am familiar with:
You can also try Pixoasis.com.
ACDSee Pro comes with an online feature (ACDSeeonline.com) that allows you to share selectively and you can choose whether to allow downloads of images, etc. Unlike the other sites you can manage your photos online from within the app.