When I was working at The Conversation, the team has has almost always had remote team members. After discussions with a colleague, Keith Pitty, we noted that using a whiteboard, or other analog ways of running a retrospective, that made it difficult to fully join in the conversation. We thought that we needed a tool to have online retro boards. Hence, RemoteRetro.
An online retro board, that everyone can log into. Throw it up on a tv/screen/projector, and only the remote team members can join in while local members are guided by a facilitator. Or, no remote team members, and use it to like a scribe to keep a record of the sprint/iteration's retro items.
Up to you. Lots of ways to use it.
It's got a bunch of common formats, plus you can customise them. It's got timers, so you can guide your team to add their items, or to vote on ones important to the team.
It also integrates into with Trello into your regular workflow by creating Action items of a retro as cards in your To-Be-Assigned queues.
Retrospectives, if done regularly, are a great opportunities to gently steer the ship as a team, with only small adjustments. New ideas, and to help solve small problems and conflicts before they become larger issues.