These two tools have allowed me to interact with HTTP, but not in the most optimal way. Poster's UI is clunky and isn't scriptable (without diving into Firefox extension internals), and Curl requires a lot of Unixy glue to process the results into something more usable than visual inspection.
I wanted something that would not only make requests, but would let me interact with the result of these requests.
When working with Evan to debug a problem one day, I mentioned my problem, and said "I really should build something that fixes this." Evan suggested that such a thing would be really useful to him, too, and that he'd be interested in working on it.
I'd planned on building my version of the tool in PHP. Evan is… not a PHP guy. He's a [whisper]Ruby[/whisper] guy.
If you've seen me speak at a conference, lately, you've probably seen this graphic:
So, Webshell was born. If you want to see exactly what it does, you should take a look at the readme, which outlines almost all of its functionality.
If you use curl, or any sort of other ad-hoc queries to inspect, consume, debug or otherwise touch HTTP, I hope you'll take a look at Webshell. It saves me several hours every week, and most of our Gimme Bar administration is done with it. Also, it's on GitHub so please fork and patch. I'd love to see pull requests.