Kerbal Engineer Redux (Legacy)
Kerbal Engineer Redux v0.6 for use with KSP v0.25 and earlier.
This plugin will allow you to view important statistics about your ship on the fly, whilst building it. Just attach the Engineer part anywhere onto your ship and up will come a nice window showing you lots of cool stuff. By popular demand the engineer has an add-on module that will also allow it to work within flight. The Flight Engineer will give you important and useful information about your vessel, surface, orbital and rendezvous flight manoeuvres.
Completely voluntary, absolutely amazing, and really does help me out a lot!