Nitrous.IO still has a free option, you have to wait for them to build it, however, so is likely not going to be helpful in the short amount of time someone will have at a meetup. It's probably still fine in the long run.
Cloud9 is free immediately for setup, and is quite easy to get going on. It's a full IDE-type environment like Nitrous, providing a RubyMine-like interface.
Koding.com is also free immediately, but takes a bit more understanding to get going. It's essentially just a virtual machine in the cloud that you can develop and test on, with an IDE-type wrapper.
As of this, I've been waiting several hours for a Nitrous.IO free space.
Nitrous.IO still has a free option, you have to wait for them to build it, however, so is likely not going to be helpful in the short amount of time someone will have at a meetup. It's probably still fine in the long run.
Cloud9 is free immediately for setup, and is quite easy to get going on. It's a full IDE-type environment like Nitrous, providing a RubyMine-like interface.
Koding.com is also free immediately, but takes a bit more understanding to get going. It's essentially just a virtual machine in the cloud that you can develop and test on, with an IDE-type wrapper.
As of this, I've been waiting several hours for a Nitrous.IO free space.