If you are posting a lot of images that you are going to want to see full-sized, the go with
http://www.pbase.com
They are free, you can download/upload over the internet, etc. It is almost idiot-proof. I should know, I have my own listing.

You can link to the images very easily. There is supposedly no limit to how many pictures you upload. I have friends that have several thousand images on their pbase accounts. I have yet to run into any problems. Downside: no copyright protection.
If you need copyright protection and want to be able to order prints, etc., try
http://www.dotphoto.com
You pay $4.95 per month, but you get 26 4x6 prints free each month, plus you can upload/download, etc. This is more for photographers who sell their images, of want to make prints, etc.
I use both of these and for different reasons.
There are many free services out there. I would recommend trying a few of the free ones before you pay.
Best of luck,
Dan