Update: The process described below works, but for most situations you probably want to use the Choice Eliminator Add-on for Forms instead.

Google Forms sign-up sheet - limits on choice options for multiple choice, check-box, or choose-from-a-list questions.  
With formRanger and a few Spreadsheet functions, when an option reaches the number of responses you set, it no longer appears in the survey...or, automatically start a wait-list for each option

formRanger works with question types Multiple choice, Check-box, and Choose from a list 

formRanger was released as an Add-on on Thursday, October 23, 2014.  These instructions refer to the Add-on.

Google Slides from my presentation at the Round Rock ISD Ninja Academy
Demonstration recipe
  1. Sign into your Google Apps account
  2. Open the demo spreadsheet with sample formulas
  3. In the File menu, choose Make a copy... and rename the spreadsheet
  4. In the spreadsheet menu bar, click Form and then Edit form
    • the form will open in a new tab
    • rename the form to remove Copy of and (Responses)
  5. Click on the Add-ons menu in the Form menu bar
    • in the Add-ons menu, if you see the formRanger menu, skip to the next step.  Otherwise, continue with installation:
      • in the Add-ons menu, choose Get Add-ons
      • in the Add-ons store window, search for formRanger
      • click on the +Free button in the list entry for formRanger
      • complete the authorization dialogs
      • the formRanger menu will appear in the Add-ons menu
  6. Leave the form tab open
  7. In the spreadsheet file, look at the Card Choices sheet
    • cells colored in green can be edited
    • cells colored in yellow contain formulas essential to the process
    • cells colored in blue contain continuation functions that must not be disturbed
  8. In the Add-ons formRanger menu, choose Start
    • the formRanger dialog window will open on the right
    • wait for the list of available questions to appear
    • check the box for the question you want to set option limits on
    • click the select menu and choose new values list
    • a new dialog window will open to allow you to select the spreadsheet
      • files are listed in order of most recently edited
    • locate the spreadsheet file for this form
    • click to select it and then click the Select button
    • choose the Card Choices sheet and the Available Options column
    • click the Next button
    • give the value list a name (e.g., Card Choice List)
    • click Save and populate question
    • in the Form, the question's option list will show all of the values in the list
  9. At the bottom of the formRanger dialog, click to turn on Repopulate questions upon form submit
The form is ready for use.  Publish the link in the usual way.  When a response is received, the Form Responses sheet and the Card Choices sheet will update and the question's options will be updated if an option's limit has been reached.