Develop Reference

In Android, how to achieve this transition effect where incoming material elements expand into view?

As per Google's material design specs, under Animation - meaningful transitions
https://material-design.storage.googleapis.com/publish/material_v_4/material_ext_publish/0Bzhp5Z4wHba3RXRFb0tRZEZDUUU/animation_meaninfultransitions_considerations_do.webm
Sometimes wish they could provide some sample codes right beside the design specs..
I couldn't find anything on google, probably because I am not sure what keywords to use.
Thanks!

The example that you linked appears to be using a reveal transition animation with a shared element between two Activities. For details on how to get your feet wet, take a look at the Android training documentation on Defining Custom Animations.

Is there a library for Floating Action Buttons (FAB) with Labels?

Is there a library for creating Floating Action Buttons with labels (similar to the Evernote app)?
Evernote Screenshot
The popular libraries seem to be
https://github.com/futuresimple/android-floating-action-button (closest to what I want... ability to expand hide "sub" actions)
https://github.com/makovkastar/FloatingActionButton (Primary function is to hide/show with a scrollview, recyclerview, or listview)
https://github.com/oguzbilgener/CircularFloatingActionMenu (library which has been around pre-lollipop)
Neither of these, to my knowledge, have this capability. Before re-inventing the wheel, has somebody already done this?

This feature request ended up being implemented in https://github.com/futuresimple/android-floating-action-button. This includes labels on both the left and right sides.
If you're interested, see the discussion here: https://github.com/futuresimple/android-floating-action-button/issues/22#issuecomment-66155108
Disclaimer: I haven't used this (yet).
I'd recommend this library over others that I've seen.

Nowadays there are available techniques of manipulating behaviour of the view that enable you to program FloatinActionButton as you want and to have joy that you have made it by yourself!
Fade in/out FloatingActionButton while scrolling RecyclerView . DETAILS
Slide down/up , beside it blog says how to:
Expand floatingActionButton and show subFloatingButtons. DETAILS HERE
There is to much details, "how to do". Therefore I've attached just links to blogs. Anyway I encourage you guys to take a look at those blogs. You will have total control over your application. Currenty I use all solutions from both blog's. Enjoy!

Especially the last library you mentioned looks quite sophisticated. To my knowledge, you can set any kind of View you want to be shown as a Button.
This View could simply be a custom-view of yours that shows an image as well as a label.

In case anyone is still looking for this functionality: I made an Android library that has this ability and much more, called ExpandableFab (https://github.com/nambicompany/expandable-fab).
The Material Design spec refers to this functionality as 'Speed Dial' and ExpandableFab implements it along with many additional features.
Nearly everything is customizable (colors, text, size, placement, margins, animations and more) and optional (don't need an Overlay, or FabOptions, or Labels, or icons, etc). Every property can be accessed or set through XML layouts or programmatically - whatever you prefer.
Written 100% in Kotlin but comes with full JavaDoc and KDoc (published API is well documented). Also comes with an example app so you can see different use cases with 0 coding.
Github: https://github.com/nambicompany/expandable-fab
Library website (w/ links to full documentation): https://nambicompany.github.io/expandable-fab/

Swipe Views in Android

I have written an Android App, which uses ViewPager to swipe between different Views of my app. This works very well, but the animation isn't like I want it to be.
The current view swipes out to the right, and the new enters from left. But I want the current view to leave like a layer to the right, so that the user can see the new view, which was "under" the current view. I want the "old" view to stay at the right side, so it can return onclick.
The current Evernote App uses this behaviour. I attached a screenshot. Thanks ;-)!
http://i.stack.imgur.com/2RlT4.jpg

You can refer Sliding-Sidebar. This has Facebook like slideout effect.
Quick reference of the above library :
You can download the Android UI Patterns app. from the Google Play and see the effects you require. Its inside ActionBar & Dashboard --> gui-sliding-sidebar.

you should use the fly in app menu here below demo project will help you
https://github.com/korovyansk/android-fb-like-slideout-navigation

I would suggest you use SlidingMenu It is a very good and solid library with an active developer. It works well with ActionbarSherlock too which is great for backwards compatibility.
SlidingMenu
An Android library that allows developers to easily create slide-in menus like in the Spotify and Facebook applications.

android button widget with a dropdown list, what is the name of this particular widget?

Im learning android layouts and Ive noticed a particular button widget in some android apps that I would like to add to my own apps, Im just not entirely sure what its called, In some cases this button widget even will include a dropdown list here are a few examples of what Im talking about.
in the first image you will notice that the checkmark, the camera and the pencil are all sitting inside of the button widget i'm after, and in the youtube app you will notice the thumbs up, thumbs down and more buttons

That's ActionBar. Native support for 3.0+ devices, and some work to do in pre 3.0-devices. You can find example in new api 14 samples(called "ActionBarCompat").

Please see my answer here which gives some good links on how to implement the "dashboard" pattern, and use the "quickaction" bar. I think this should put you on the right path. Also there is a link on how to implement the "action bar."
EDIT: According to Mighter, if you use API 1.6 - 2.3 there should be official Google samples for this now. Please see this.

Android sidebar

I've been using firefox for Android and really like the use of the sidebar to hold shortcut icons and the like. How would I go about creating a similar bar myself with the following attributes:
progressively revealed as I swipe in one direction
progressively hides as I swipe in the other direction
can be a custom width
I can dynamically inject layout in to it or it can hold static content
Is there any open source code available? If not, what approach would I use to create this?

Sound like you're describing a Gallery control. There are some examples in the ApiDemos project here.

The first part can be solved by using a ListView. The second part I don't know yet. I'm looking for such a component as well.