I have a drop down list that has a value 'any'. And I have this code in controller...
@results = Post.find(:all, :conditions => 'status = ?', @status)
There is no such value.
If any is selected, it means search for all records. What do I need to put in variable @status to make so that it would search for all.
I can have multiple drop down lists in future with many combinations so I cannot if statement here.
Oh yes you can 
You just need to build up your conditions parameter bit by bit, eg
conditions = {} if @status != 'any' conditions[:status] = @status end
if @foo != 'any' conditions[:foo] = @foo end
@results = Post.find :all, :conditions => conditions
You probably want to put most of this in the model.
Fred