Update 6 September, 2015: Google "Blue Dots" are back and E Kreative has created a Pano ID Extractor tool that allows you to retrieve a photosphere ID. This is a great tool as we can now use the id in the embed code to circumvent the lack of the embed option in the share menu. In the post below I've added in information on how to use the Pano ID Extractor tool.
Note: at the moment this only works with photospheres uploaded before the demise of Map Views
With the shuttering of Google Map Views and the release of Contributions the ability to embed Photospheres and to create and embed Constellations has, only temporarily I hope, disappeared.
For those who had published Constellations or Photospheres before the demise of Map Views and need to embed them now don't have the embed option available in the new Google Maps.
I've researched the problem and the good news is that they can still be embedded into a webpage. The Nat Geo Orion tour constellation, created before the closing of Map Views, was just published, using the old embed code and a retrieved Pano ID.
Note: Google may change, delete or stop access to this old data at any time, so no guarantees that it will always work.
Current state of Contributions
When I first go to my contributions sidebar I see a number of photospheres that I can scroll up and down through. In this example what was previously a constellation of 5 images is now displayed as a group of 3 images under the title Banda Sea. Scrolling further down will reveal the other 2 images also under the title Banda Sea. They are separated because of the date they were originally published. Sorting in the sidebar is always by date, latest first.
If I select the first image the photosphere loads, the sidebar disappears and I can move the image and see the constellation navigation arrows.
Using the arrows allows me to move through the constellation as normal. Unfortunately if I want to embed the Constellation in a web page when I select the Action options (the 3 small dots in the information panel) and then Share or Embed there is no embed option!
Retrieving the Pano ID
1. Open the Pano ID Extractor tool and zoom to a location where your photosphere is located
2. You will have to keep zooming in to the map until you are very close to the location (on normal maps it's approximately a zoom of 15) Keep checking by dragging out Peg Man until you see the blue dot
3. Once you are close enough dragging Peg Man onto the map will reveal the blue dot and hovering over it reveal the photosphere preview
4. Once you have the right Photosphere selected release the mouse to drop Peg Man and the photosphere is displayed in a split window.
5. Copy the Pano ID (red)
1. Take the Pano ID, in this case DBquXRNtK30AAAQfCWCNMA, and replace "PanoIDHere" with it in the code below
<iframe width="100%" height="480" frameborder="0" scrolling="no" marginheight="0" marginwidth="0" src="https://maps.google.com/maps?layer=c&panoid="PanoIDHere"&ie=UTF8&source=embed&output=svembed&cbp=%2C0%2C0%2C0%2C0"></iframe>
2. You can now embed this into your webpage as I have done above.
3. To set the Pan, Zoom and Tilt of your initial view modify the section of code %2C0%2C0%2C0%2C0. For example to orient the view for the photosphere above my settings are %2C359%2C%2C%2C30 - the first value is pan, the second I haven't figured out yet, the third is zoom and the fourth is tilt.