I've found one of the best to be the one I'm using, Smugmug.

Their Basic account is $29.95 US per year, and is what I have. It allows Unlimited storage, and up to 2GB/month of transfer. I have several hundred shots loaded there - full scan files - so am able to use it as a full online archive. I'm getting about 16,000 hits a month, which is only using 10% of the bandwidth allotment, so there's a ton of capacity.

Go check out my setup: http://clemmie.smugmug.com

Viewers can select from four view sizes, including the full original scan, and can download any of them. They can also order prints direct from the service - though it may be cheaper to just download the file and have them done locally.

If you decide to sign-up, read my bio page there first - which will tell you about how to save $5 on your first year's service, while helping me cover next year's. (Nice little referral program they have going.) Then click on the 'Free Trial' link at the top of the page to sign up. First 7 days are free, then they charge your card for $29.95 ($24.95 with a 'referrer') and you're set for the first year.