Viewing photos on your Kindle? Yep. One built in way and/or a couple conversion apps...

A Kindle World blog - Kindle Pictures Feature. .2 Free Tools that Convert Images to Kindle format.

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Your Photos on your Kindle in the Pictures Folder - a Kindle Feature
In the meantime, Kindle owners CAN put favorite photos or illustrations on the Kindle in a special Pictures folder, and I've found that many don't know this is possible.

Remember that Kindle books or files can be Searched for words like "pictures" and sometimes that makes it easier to find a feature.

A Kindle customer posted step-by-step instructions at the Amazon Kindle forums. In reply to an earlier post on Feb 9, Anthony Hansen wrote (slightly modified) :

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KINDLE IMAGE CONVERTER
This is a nicely easy-to-use tool that converts almost any image you have (size does not matter much) to a Kindle-compatible black & white version in the right size and orientation for the Kindle display. It works for 6" Kindles and the 9.7" Kindle DX's.

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E-NKI MANGA, COMICS, AND GENERAL BULK IMAGE CONVERTER FOR KINDLE
I haven't had a chance to try this one. E-nki describes it this way:

"E-nki is an image processor designed for latest Kindle.
"It converts common image documents (JPEG, PNG, GIF, BMP) into optimized PNG files for e-ink displays, and more important, you can convert your compressed archives directly. (CBR and CBZ too!)

There is also a link to the FAQ, which does answer questions not addressed on the main page. E-nki is a downloadable file and there's no web-style conversion tool.

On what, specifically, the utility does:
1) Converts pictures to grayscale
2) Tries to remove white borders
3) Resizes pictures while maintaining the aspect ratio
4) Rotates the pictures

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Yep, I'm one of those people who didn't know that the kindle could natively view image files (like JPG's, PNG's, GIF's, etc). I mean I knew it could render them, having seen any number of images in books, etc, but I didn't know that if you put those images files directly on the kindle, in a pictures folder, that you could view them natively...

Sure they are in not in color, but still I thought this "hidden" feature kind of neat.