Instagram (for iPhone)

You can't use instagram without signing up for another social network. It would be nice if you could just use your Facebook or Twitter account to sign in, but no such luck.

Don't worry, this doesn’t mean you'll get a notification every time a contact uploads a photo, but you will if they comment or like one of your images.

As in Twitter, you "follow" other users whose photos, comments, and likes you want to know about. You can populate your followed list from your Facebook and Twitter.

Instagram suggested I follow these users, includeing Rosie O'Donnell.

You get a choice of 16 effects, such as sepia and lomo, plus a tilt-shift option that adds bokeh.

You can view the most-liked recent photos on the service.

Here's where you see you followeds' photos, and where you can like or comment on them.

News is also sort of a feed, but just shows recent uploads and likes by your followeds and activity on your own photos.