Lots of links:
Some nice and free icons.
A very simple and nice calendar generator for Ruby on Rails: CalendarHelper.
Putting REST on Rails
Curing Float Drops and Wraps
Fixing the IE Float Drop Bug
Centering a block or image
Rails geocoding and Google Maps
Create your own AJAX effects - From Thomas Fuchs himself.
How to quickly do authentication with LoginGenerator.
Some very nice pictures of Rainbows.
Star clusters in the Small Magellanic Cloud
Some links for uploading files with Ruby on Rails:
HowtoUploadFiles from the Ruby on Rails wiki