Salesforce.com's been talking a lot about cloud computing lately, but its own data center doesn't match the size of its ambitions. So, where would the additional infrastructure come from? The clouds created by this question cleared up a bit today with the unveiling of Salesforce.com's new big buddy: Amazon Web Services.Salesforce.com announced today its "Force.com for Amazon Web Services" will leverage the "database, logic, and user interface features of Force.com and the storage and compute capabilities of Amazon S3 and Amazon EC2 services." What that means is Salesforce.com is looking for developers to use its platform to write applications that are partly hosted by Salesforce.com, partly hosted by Amazon's server and storage systems. Salesforce.com says developers' apps will be able to "seamlessly span both clouds," but exactly how that will work remains, er, cloudy to me.

Salesforce.com did explain it will have a toolkit for developers that makes the API for Amazon's hosted storage service (S3) available within Salesforce's Apex code. Developers will be able to add, remove, and modify Amazon S3 objects as needed by their applications. The use of Amazon's S3 services might appeal to developers building Force.com apps that require the storage of images, videos, and other big files.

Another offering is a toolkit that lets developers extend their Force.com applications with existing programming languages, such as PHP or Ruby, or pre-existing executables and libraries, to run in the Amazon Elastic Compute Cloud (EC2), Amazon's hosted server service that lets you use only the computing power you need on any given day.

There's still much to be answered here, including how much and to whom a developer or independent software vendor would pay in this Salesforce.com/Amazon co-hosting scenario. But the partnership does show that Salesforce.com sees Amazon as a way to solve some of its infrastructure issues as it tries to become more of a "cloud computing" provider.