You can now embed Street View imagery and photospheres in the new Google Maps. Find the Google Maps imagery you want to embed, click the gear button at the bottom of the page, pick "share and embed image" and copy the code generated by Google. Google lets you change the size of the embedded image and preview it.
Here's an example from Googleplex:
Google also added support for Street View and photospheres to the Google Maps Embed API. "These embeds use the new imagery viewer technology that powers Street View in the new Google Maps. Embedding a Street View or Photo Sphere works similarly to the Street View Service in Google Maps JavaScript API v3 - specify a lat/lng or panorama ID to pick your location, plus heading and pitch to determine direction of the scene and angle of the camera," informs Google.
{ via +Google Maps }
