You can run netcat in the "listen" mode:
nc -l 8080
This will listen on localhost:8080, dump everything that comes in to stdout and reply with data from netcat's stdin. This is useful for a quick and easy HTTP testing - you can initiate a request and paste the response you want into the console.
Is there something similar that can be used with HTTPS? Preferably something cross-platform that's likely to be installed on most systems.