@tomnomnom's anti-burl with some added functionality. No really, It's mostly his work. Thank him.
Inspired by TomNomNom's antiburl. This takes URLs on stdin, checks their response status code against a supplied code (or list of codes) and outputs matches.
go get -u github.com/raverrr/dantiburl
cat urls.txt | dantiburl
-c Concurrent jobs (default 50)
-q Quiet mode. output only URLs
-s Status code to filter for. Can be set multiple times. (Default: <= 300 and >= 500)