It’s never been easier to do file uploads with MongoMapper and GridFS. Joint, from MongoMapper creator John Nunemaker, is a MM plugin that adds some nice convenience methods to your models:

class Foo
  include MongoMapper::Document
  plugin Joint

  attachment :image
  attachment :pdf
end

By declaring these two attachments, you automagically get accessors for image and pdf. The setter methods take any IO (File, Tempfile, etc) and the getter methods return a GridIO type from the Ruby driver.

John even throws in some nifty proxy goodness:

doc.image.id
doc.image.size
doc.image.type
doc.image.name