Using Tags (An active record model) to find tags by the tag property:
Tag.find_by_tag("Ruby") Ruby Tag.find_by_tag(["Ruby", "Gem"]) Ruby
That did not return what I expected, find_ returns one object by default. first_ last_ or all_ modifiers can be used. So to find multiple tags by the same property:
Tag.find_all_by_tag(["Ruby", "Gem"]) Ruby Gem
Again with slightly less active record magic:
Note the = ? for singular items and IN (?) for a list of items.
Tag.find(:all, :conditions => ["tag = ?", "Ruby"]) Ruby Tag.find(:all, :conditions => ["tag IN (?)", ["Ruby", "Gem"]]) Ruby Gem
More info can be read on Rails Guides.