Best Cloud Service?

I'm looking to back up my half terabyte or so of photos to the cloud as well as about another half a terabyte of videos. But I really don't know what the best service is to go with.

I'm a mac user who also uses windows machines from time to time, so access from those windows machines would be a bonus. My main machine is a mac and the external drive I store my photos/videos on is mac formatted.

My video files are mov and m2t files from my GH1, as well as some old DV tapes I plan to capture soon that I would also like to back up. So I'm looking at probably a terabyte or more of storage space needed total. Maybe a little more as my library grows.

Price is an issue. I don't want to pay hundreds of dollars a year, but $120 is about what I am comfortable with. Give or take some.

Any suggestions?