Dropbox let’s you move your files to the drop box it creates on your computer to share and store files online and keep files in sync across your computers, online and offline. Also allows for easy sharing of folders and auto creation of slideshows. 2GB storage limit, works on Windows and Mac OS X, currently in private beta.

Foldershare is a service that allows automatic file synchronization between your personal computers by sharing any folder and allows file sharing with others. Formerly ByteTaxi Inc, acquired by Microsoft. File size up to 2GB, no storage limit. Works on Windows and Mac OS X.

Jungle Disk let’s you store files and backup data securely to Amazon’s S3 Storage Service. No syncing and therefore no offline access. It does offer some sort of backup option but the interface is confusing. Unlimited storage for 15¢ per GB on Windows, Mac OS X and Linux. Without syncing it still allows you to open, edit and save files seamlessly.

S3rsync syncs your files to Amazon s3 platform using rsync bandwidth efficient algorithm that enables to upload only partial files that were changed. Not tested yet. Unlimited storage in 10GB buckets for 15¢ per GB and an unknown fee for the software and service. You can also get the storage directly from S3rsync instead of Amazon. Testing as soon as I get invited for the private beta.

Are you aware of any more options? Please let me know in the comments.