From the blog:
Today we are thrilled to announce the global availability of OneDrive. For our existing SkyDrive customers, you are all set; your files are ready in the new OneDrive experience. All you have to do is head over to www.OneDrive.com and log in. For those of you hearing about the service for the first time, OneDrive gives you one place for all of your files, including photos, videos, and documents, and it’s available across the devices you use every day.
OneDrive's new storage bonuses come in two forms. 5GB of bonus space will be available via referrals, with a bonus of 500MB for each user referred to OneDrive (up to a maximum of 10 users) and a further 3GB of space will be available by backing up (syncing) photos from their camera roll using Windows Phone's built in functionality (or using the OneDrive app on Android or iOS). If you have Windows Phone's built-in upload to to SkyDrive (OneDrive) feature turned on you'll earn this second bonus automatically.
If the bonus storage does not give you enough space it is possible to buy additional storage space. For the first time there are now monthly payment options for Microsoft's cloud storage service with plans starting at $4.49 per month for 50GB and going up to $11.49 per month for 200GB.
As before it is also possible to pay for extra storage via an annual payment, which offers better value that the monthly plans. Adding 50GB costs $25 per year, while adding 100GB costs $50, and 200GB costs $100. The extra purchase space is in addition to any bonuses or special offers you may already have associated with your account.
The monthly prices for OneDrive are a little more expensive that those for Google Drive ($9.99 per month for 200GB), but the annual plans remains better value. Both OneDrive and Google Drive are significantly cheaper than DropBox ($19.99 per month or $199 per year for 200GB of space).