Twtgal allows you to upload multiple pictures and then tweet a shortened URL to share them as a gallery. A great way to show off a set. You could simply make a collection on Flickr or other photos service and use some short URL for that gallery, but not every one would get that either. The site itself summarizes the service as:
Just upload your pictures, get short url for the gallery, tweet it!
Your first tweet with gallery url will be imported and shown on the gallery page. Last 20 tweets about your gallery will be shown below the images. You can set the style of the gallery and few other options
I didn’t upload a set as most of mine are already on Flickr. The bonus of the site was the lack of the requirement to provide them your Twitter password. You can bookmark the admin link to your uploaded gallery to be able to get back to manage it. You can upload a maximum of 14 images in the free account with 2mb limit for each picture. Images all get resized to 800×600.
The site is ad supported and allows the galleries to be browsed or played in a slideshow. Lastly you can also email pictures in and get a reply with the link for the gallery.