Yeah, I too would like a ship building queue. Rally points as suggested above are only a partial solution.
1. Rally points are only effective for building a fleet or group of ships that are being built by different planets...and you don't care how far apart they are.
2. But Rally Points are not effective if the ships must come from widely dispersed planet starports, especially if it's still early in the game and I haven't discovered warp drive or extensive miniaturisation (sp) yet.
3. Sometimes, I have one corner of the galaxy producing ships that will only be used in that same corner, due to the expected travel time, or in other scenarios, I have a lower density of habitable (or lower class) planets, which make rally points even less effective.
So it would be nice to pre-plan what ships each planet should build, and how many. I would also like (for each planet) an independent "continue to build last ship" option, or a "prompt when queue empty" option.
Sometimes, it's okay to just keep building constructors or colony ships indefinitely.
Other times, however, I would prefer to program a "stop" command and get notified when the end of the queue has been reached for a given shipyard/starport, so that I can be physically reminded to review that planet or section of the galaxy and establish a new queue.