I think this is actually pretty rare. I think the Yahoo system used to do this, but pbase, flickr, zenfolio, and picasa don't require registration. Note that on most you can password-protect folders for some privacy..
I selected to use pbase ($23 a year), because I really liked how they organize images by equipment, which helps in product research..
Everything I write is a personal opinion. Even when I quote facts, they are the facts I personally choose to accept.http://www.pbase.com/mariog..
There are thousands of image hosting services at the moment, I think. Even if you're only interested in those which allow organizing into albums, there are still an awful lot..
Some give you the option of requiring an sign-in or not. Those that don't, are essentially relying on security by obscurity i.e. sharing the (preferably unguessable) link to an album is equal to sharing the link + password that another site might require. Those that allow you to require a sign-in might, in theory, offer more security if the terms are fairly steep (paying membership, sharing login information is a bootable offense, that sort of thing otherwise, one could share that login and still grant access to the album)..
I shouldn't be all that specific in recommending services, for various occupational reasons, but just note that there are many, and that you may need narrower criteria if you to narrow things down. For instance, if you want tagging, public image pools, guestbooks for comments, the ability to sell prints, organizational capabilities wrt info in EXIF, large or essentially-unlimited storage capacity, large or essentially-unlimited transfer per month, pay vs. ad-supported, the ability to freely hotlink images onto other forums or your own web pages... these aren't necessarily universal...
To add to what Mario said Zenfolio certainly does not require registration. You can password protect individual photos or whole galleries of them. You can lock the original photo or make them available for download and many other options besides..
I think you will find that any that require registration to view will make it impossible to post by link here..
*Nikon* D Eighty + Fifty - Other equipment in Profile.
Another zenfolio fan/user here..
I'm very happy with it. For $40 (US), you get unlimited pics and space, easy uploading, a great slide show, gallery and photo level access options, and a very professional and polished looking presentation for your pics..
They are still "relatively" new, and will be adding more features in a few months according to their support folks - which by the way, I have found customer support to be very prompt and personal in their e-mail replies..
But check out the different sites, and see which one appeals to you. Other major players are pbase, smug-mug, flicker, and I'm sure there are more. Just do a search .
Btw, zenfolio has a free trial with no credit card needed for trying it out..
Image control:Zoom outZoom 100%Zoom inExpand AllOpen in new window..
I like Smugmug !!.
BigDog Ken Griffith.
Sunny Westchester, NY..