Gistit is a bashscript for instantly uploading selected text to github and placing the url to that gist in your clipboard. It relies on curl, xclip, python, sed, grep and notify-send. Use f.i. xbindkeys-config to add a keybinding to the script and you've got instant sharing. The script takes one parameter which is a OAuth token for github.

gistit.txt

#!/bin/bash

if [ $# -eq 0 ]
  then
    echo "No OAuth token supplied. Create one with: "
    echo "curl -u 'YOUR_GIT_USERNAME' -d '{\"scopes\":[\"gist\"],\"note\":\"Help example\"}' https://api.github.com/authorizations"
    echo "Use the token value that is shown in the json output."
  else
  	URL=$(xclip -o | python -c "import sys, json; print json.dumps({ 'public': True, 'files': { 'gistit.txt': { 'content': sys.stdin.read() } } })" | curl -H "Authorization: token $1" https://api.github.com/gists -d @- 2>&1 | grep -E '"html_url": ".*gist.*' | sed 's/.*html_url": "\([^ ]*gist[^"]*\)",/\1/')
  	echo $URL | xclip -i -selection clipboard
  	notify-send --category="transfer.complete" "Gist uploaded" $URL 
fi