XML Cleansing
When writing XML, all text should be converted to UTF8 if it's not coming from a known source. This blog post provides a ruby function to do the conversion.
Secure UTF-8 Input in Rails - igvita.com
don't trust incoming UTF-8 input in rails
Shades of Gray: Articles in Character Encodings
Series of blog posts by James Earl Gray II on character encodings and ruby
Shades of Gray: Bytes and Characters in Ruby 1.8
some excellent advice on using UTF-8 in ruby 1.8
Encoding issues with Ruby 1.9 and Rails 2.3
rails 2.3 marks all active record attributes as encoded in "ASCII-8BIT", regardless of what is in database.yml.
#2476 ASCII-8BIT encoding of query results in rails 2.3.2 and ruby 1.9.1 - Ruby on Rails - rails
How do I replace accented Latin characters in Ruby? - Stack Overflow
How to port your gem to Ruby 1.9 - 世界線航跡蔵
Ruby 1.9 character encoding field notes · Fingertips
The biggest problem with receiving data from external sources is trust. Sources can lie about their encoding or provide broken data. Sometimes it gets mangled accidentally and sometimes someone is attacking your application with a carefully crafted payload.
Soapbox
interesting rant about ruby 1.9's encoding support. Most it it resonates strongly with my opinions.
Ruby 1.9 Encodings: A Primer and the Solution for Rails « Katz Got Your Tongue?
Another clear summary of the encoding mess of 1.9. With great power comes great ways to shoot yourself in the foot.
From Iconv#iconv to String#encode
Twitter / JEG2: A neat Ruby encoding trick
A neat Ruby encoding trick from @arcandros: open(…, "r:bom|UTF-8")
removing illegal bytes for encoding in ruby 1.9+ strings | Bibliographic Wilderness
Ascii-ization transliteration built into ruby I18n gem in Rails | Bibliographic Wilderness
Rack/Ruby on Rails: ArgumentError: invalid byte sequence in UTF-8 | Running with Rails - Dev Blog not only for Rails fanatics!