Issue TODO is a chrome extension that quickly copies a github or Jira issue to your clipboard so you can paste it into your code as a TODO. It also includes a link to the issue and author for easy reference and will put you right in the comment field when you visit a github issue, so you can immediately join the conversation.
HubDesk lets you receive and respond to emails with Github issues. HubDesk creates issues for each new inbound email thread and you can respond to the sender with an issue comment that starts with **@reply**. It can be used for bug reports or as a help desk.