What is the difference between Ubiquitous Computing and Cloud Computing? Are these the same things? Which one came earlier than the other? And what are the similarities if there are any?
My understanding is, ubiquitous computing refers to every day objects becoming computing nodes, such as smart appliances. Cloud computing refers to running applications on the internet rather than locally. Services like Gmail and Flickr are examples of consumer cloud computing. Rather than reading mail or storing photos on their own machine, people can do these things on the internet instead. See Wikipedia for more detail.
I don't understand what you mean by "come before" the other. Both of these concepts have been floating around for years as ideas, sometimes under different names. Cloud computing is something that is already put into practice. Ubiquitous computing is emerging, but not widely deployed.
These concepts aren't directly related or particularly similar. Ubiquitous computing is about adding computing to everyday object and activities, Cloud computing is about hosting services.