I've been using Picasa Web Album most recently. I don't know what their exact policy on adult content is, but Google is usually pretty liberal and it's very easy to use and hotlink to. I find it to be much easier than Flickr (which does allow adult images, provided they are marked Adult/mature when they're uploaded) and just as simple as any number of free hosts online.
If you want to make some of your albums public and some private, try PimpAndHost.com. If you don't mind making everything public - meaning you can look through everybody's pics and they can look through yours - take a look at G-Pic.com. Both generate the "image tags" for you. Both are free.
PimpAndHost has more features even if you don't register, the interface is more pleasing to the eye, and it also lets you hotlink to a full-sized image. At G-Pic you must register to upload your pics. Its hotlinks are to oversized thumbnails, but if you click the image, it takes you to the full sized pic.
Here's a sample of the G-Pic oversized thumbnail...
Try www.flickr.com
you have to have a yahoo account and you can set up your own photo album
Keep pics private or make them public and adult
Other good sites are
Talk Dirty to Me
Show Me your wife
Wifelovers