Add user link helpers that don't need an instantiated user.

app/helpers/application_helper.rb

@@ -1,2 +1,9 @@
 module ApplicationHelper
+  def username_program_slug_path username, program_slug
+    "/users/#{username}/programs/#{program_slug}"
+  end
+
+  def username_path username
+    "/users/#{username}"
+  end
 end

app/views/programs/index.html.haml

@@ -26,5 +26,4 @@ Here it is: every single program we've got. Check them out!
 
 %ul
   - collection.each do |program|
-    - user = User.find_by_username(program.author_username)
-    %li #{link_to program.title, user_program_path(user.username, program)}, by #{link_to user.username, user_path(user.username)}
+    %li #{link_to program.title, username_program_slug_path(program.author_username, program.slug)}, by #{link_to program.author_username, username_path(program.author_username)}