Some helpful links:
http://appinventor.mit.edu/explore/get-started
http://ai2.appinventor.mit.edu/reference/components/userinterface.html
App merger
http://appinventor.mit.edu/explore/sites/all/files/Resources/AIMergerDocumentation.pdf
Change background
https://search.yahoo.com/yhs/search?p=app+inventor+change+background&ei=UTF-8&hspart=mozilla&hsimp=yhs-002
App Inventor's FAQ help site
http://www.appinventor.org/content/howDoYou/eventHandling
Energy Meters (mostly for games)
https://www.youtube.com/watch?v=KTlmHjLlRo0
Scores
http://appinventor.mit.edu/explore/ai2/molemash.html
Drawing and Animation - sprites, balls, and canvas
http://ai2.appinventor.mit.edu/reference/components/animation.html#ImageSprite
Lists
http://beta.appinventor.mit.edu/learn/reference/components/basic.html
http://beta.appinventor.mit.edu/learn/reference/blocks/list.html
https://search.yahoo.com/yhs/search;_ylt=A0LEVu7KVGBW.kgAIronnIlQ;_ylc=X1MDMTM1MTE5NTY4NwRfcgMyBGZyA3locy1tb3ppbGxhLTAwMgRncHJpZANaOFpzN0RiVlNLS1hRbE5KRm9XV25BBG5fcnNsdAMwBG5fc3VnZwMxMARvcmlnaW4Dc2VhcmNoLnlhaG9vLmNvbQRwb3MDMARwcXN0cgMEcHFzdHJsAwRxc3RybAMzMgRxdWVyeQNhcHAgaW52ZW50b3IgbGlzdCBwaWNrZXIgcmVtb3ZlIAR0X3N0bXADMTQ0OTE1Mzc0NA--?p=app+inventor+list+picker+remove+&fr2=sb-top-search&hspart=mozilla&hsimp=yhs-002
https://sites.google.com/site/blocks123/lists
Contacts
http://appinventor.mit.edu/explore/ai2/piccall.html
http://beta.appinventor.mit.edu/learn/reference/components/social.html
Quiz
http://appinventor.mit.edu/explore/ai2/quizme.html
Media
http://ai2.appinventor.mit.edu/reference/components/media.html
Layered Sprites
http://appinventor.mit.edu/explore/ai2/molemash-2.html
Colors
http://appinventor.mit.edu/explore/app-inventor-color-chart.html
https://joners-inventor.appspot.com/learn/reference/blocks/colors.html
Writing on screen with finger
http://www.appinventor.org/content/ai2apps/simpleApps/paintPot2
Multiple screens
http://cs.wellesley.edu/~eni/aitutorial/multiplescreen.html
http://theunlockr.com/2010/09/01/google-appinventor-how-to-create-multiple-screens-for-your-app-as-best-we-can/
Sensors
http://appinventor.mit.edu/explore/content/location-sensor.html
http://ai2.appinventor.mit.edu/reference/components/sensors.html
Computing distances between points
https://www.youtube.com/watch?v=6mHyGm-HGwA
http://appinventorblog.com/2010/09/30/computing-distance-from-gps-points-in-app-inventor/
http://forums.androidcentral.com/android-app-inventor/277517-manual-distance-quick-distance-measuring-app-new.html
Accessing Contacts
http://beta.appinventor.mit.edu/learn/tutorials/textgroup2/textgroup2.html
How to publish your app
http://www.androidworld.it/forum/app-inventor-91/%5Bhow-%5D-publish-app-created-app-inventor-android-market-4597/
Tiny DB
https://www.youtube.com/watch?v=A7m3OvNkF4M
https://sites.google.com/site/blocks123/tinydb
Adding and Removing members from a Text Group
http://appinventor.mit.edu/explore/content/text-group-part-2.html
Changing from a jpeg to png file
http://www.wikihow.com/Convert-JPG-to-PNG
http://www.zamzar.com/convert/png-to-jpg/
Saving a png file with a clear background
https://social.msdn.microsoft.com/Forums/en-US/e3e347b5-4f75-4b1b-8dd8-54b6aea0da76/saving-a-png-file-with-transparent-background?forum=Vsexpressvb
http://www.makeuseof.com/tag/3-easy-ways-to-remove-backgrounds-from-images-without-specialized-software/
Mutator Blocks
appinventor.mit.edu/explore/ai2/support/concepts/mutators.html