Ruby 2.0, 42 chars

gets.chars.each_slice(2){|c,n|$><<c*n.to_i} 

Ruby 2.0, 41 chars

(a=gets.chars).each{c,n,*a=a;$><<c*n.to_i} 

Shows an error after the string has been printed; Run it with something like ruby runlength.rb 2>/dev/null if you mind.

Ruby, 30 bytes

gsub!(/(.)(.)/){$1*$2.to_i} 

27 bytes code + 3 bytes to run it with the -p flag:

$ ruby -p rld.rb <<< ":144,1'1" :4444,' 

Ruby 2.0, 42 chars

gets.chars.each_slice(2){|c,n|$><<c*n.to_i} 

Ruby 2.0, 42 chars

gets.chars.each_slice(2){|c,n|$><<c*n.to_i} 

Ruby 2.0, 41 chars

(a=gets.chars).each{c,n,*a=a;$><<c*n.to_i} 

Shows an error after the string has been printed; Run it with something like ruby runlength.rb 2>/dev/null if you mind.

Ruby, 42 chars

gets.chars.each_slice(2){|c,n|$><<c*n.to_i} 

Ruby 2.0, 42 chars

gets.chars.each_slice(2){|c,n|$><<c*n.to_i}