I've been doing ruby on rails development building a web app for 3 months now and use the below which weren't too hard to pickup and assist noobs like us.

iTerm2 terminal replacement http://www.iterm2.com/#/section/home

SublimeText editor http://www.sublimetext.com/

Solarized themes (terminal defaults burn your eyes out) http://ethanschoonover.com/solarized

Keyboard-based window moving/resizing tool http://www.irradiatedsoftware.com/sizeup/

If you're planning on doing Ruby on Rails web dev then get this 1-click installer to simplify setup: http://railsinstaller.org/