Is there an equivalent of Silverlight?

Moonlight is an open source Silverlight implementation written in Mono. You can download it here: http://www.go-mono.com/moonlight/

pipelight released and we can use it for silverlight as a best alternative moonlight.

to install that open your terminal and type as

sudo apt-add-repository ppa:ehoover/compholio
sudo apt-add-repository ppa:mqchael/pipelight
sudo apt-get update
sudo apt-get install pipelight

Pipelight is the best alternative to Silverlight plugin in Ubuntu. Just open the terminal and add the following repository:

sudo add-apt-repository ppa:pipelight/stable
sudo apt-get update
sudo apt-get install pipelight

There is no need to do anything else. The installed plugin should appear among addons in your Internet browser and you should enjoy watching silverlight videos :) I have tested it in Firefox.