I'm currently writing a mashup between my company's service and salesforce and I need to encode the data which I am sending to our service in base64, but I can't seem to figure out how to do this in Apex.  Can someone please point me in the correct direction.

Thanks

I have a custom setting that I want to be able to see the value of via the API.

"Custom settings that have Privacy defined as Public are exposed to the API in the same way custom objects are exposed."

But how do I match that to the user I'm logged in as?  It's not like the Id's returned are the same as ProfileIds.