Plugin recommendations: acts_as_file and acts_as_image.
File column is outdated (isn’t it? Haven’t touched it for ages), attachment_fu is sorta heavy (Amazon S3? WTF?), and rolling your own requires skills.
I’m using acts_as_file and acts_as_image, both written by Tore Darell, and they work great. They’re simple and un-bloated, with few features.
Recommended.