Merubi

Too cheap to buy an external harddisk but wants to backup your photos? Try these free online storage.

Shutterfly
“Our picture storage is free and unlimited. We never delete photos.”

Snapfish (SG)
Upload, share or order. Receive them within 2 working days (Singapore).

Flickr
Formerly Yahoo! photos. Easy to use.

Photobucket
Allows you to link your pictures to forum posts.

Picasaweb by Google
Limited online storage capacity (for free accounts) but easy to use Picasa image editor & face detection capability.

Webshots

Picnik
Allows you to connect to popular photo storage websites to edit your photos stored in your online account.

There are probably many more others out there, but do you really have that many photos?