Casius Durling published an insightful post describing five simple refactorings to improve the readability of Ruby code. I found 'Multiple equality comparisons' the most exciting.

It starts with a common expression simillar to this one.

foo == "bar" || foo == "baz" || foo == :sed || foo == 5

And after the refactoring it now looks like this.

["bar", "baz", :sed, 5].include? foo

19 less characters to type and it is now declarative instead of imperative. Another bonus is the increased ease of change. Now there is only one copy of foo.