I paid for an account on Flickr. Unlimited storage. Usage is measured in bandwidth, e.g. upload and download by viewers - 2GB per month. Good for organising your photos into sets. However, as long as your photos are marked as public, anyone who chanced upon your site can see all of your photos. Your photos marked private can only be seen by Flickr memebers, means your friends and family members need to register on Flickr.
I find Imageshack is good for say linking to a single or few pictures, just cut and paste the provided URL. But their interface isn't as good as Flickr.
I tried www.zoto.com recently to upload photos of some highschool reunion event. Pretty nifty. Has a batch-uploader program. Unlimited bandwidth and 2GB account for even the free membership. I have no experience with Flickr but I use Photobucket and Imageshack for limited hostings (mostly for display in this forum!).