"In the cloud" - You can use this phrase to say that a resource is part of the cloud.
For example: "machine 1234 is in the cloud" or "the application was deployed in the cloud".
"
On the cloud" - You can use this phrase to say that you're writing about a specific cloud.
For example: "my post on the Amazon cloud" Google Results 560K for "deployed in the cloud" 249K for "deployed to the cloud" 236K for "deployed on the cloud" 10K for "deployed into the cloud" 1.1M for "machine in the cloud" 347K for "machine on the cloud" 2.5M for "application in the cloud" 1.3M for "application on the cloud" 3.3M for "running on the cloud" 3.2M for "running in the cloud"
english.stackexchange.com/users/212/b.roth
I suspect the phrase originated in the habit of drawing the internet as a cloud shape on network diagrams.
Diagramming products such as Visio provide cloud shapes in their network diagram templates.
Since servers are then drawn inside the cloud shape, the phrase in the cloud is a better reflection of the diagrammatic usage.
Anyway, clouds are insubstantial things unable to bear the weight of a cluster of big-iron servers attempting to perch perilously on top.
Much better to nestle your servers in the warm fuzzy nurturing embrace of the cloud whose opaqueness hides them from nasty predators.
Images from Wikipedia
english.stackexchange.com/users/2614/RedGrittyBrick
In this case, it would be “in the cloud”.
english.stackexchange.com/users/2995/Mathias Bynens
"On" the cloud - could be taken to mean that you are on the cloud of cloud computing taken in context of "I am on cloud nine" "
In" the cloud - seems to convey that you are right in the midst of all the latest happenings in the cloud computing space.
I don't think that there is a specific right or wrong here.
It depends on the general direction / viewpoint that your blog is trying to convey.
Considering the morass that usually surrounds a term like "Cloud Computing", "Demystifying the Cloud" might also not be a bad option!!
english.stackexchange.com/users/2761/Jagmag
"In the cloud" is where your data is stored, or where your processing takes place, in the cloud computing paradigm.
"
On the cloud" might however be a nice blog title.
It means you are writing "on the cloud", where "on" means "regarding".
You are writing on "the cloud" as a concept, so there is no need to pluralise, even though you will doubtless write about a number of different "clouds".
See Stephen King's "On Writing", Carl Rogers' "On Becoming A Person", John Scanlan's "On Garbage".
english.stackexchange.com/users/3626/slim
@Bruno - I thought we say 'the application was deployed to the cloud' instead of 'in the cloud' Edit: Added answer
- I think it best to use 'on' or 'in' or 'to' depending on the context.
If you are going to say '...
is running on the machine' , ' ...
is running on the cloud' , '... is deployed to the machine' , ' ... is deployed to the cloud' ,
english.stackexchange.com/users/2054/Sairam
Considering that in the body of the question you have not started the phrases with a capital letter, is it to be presumed that the phrase is only a part of the blog title?
In that case, a lot can depend on the full blog title.
However, a short 'On the Cloud' would be nice, both grammatically as well as technically.
(note the capitalization again, the Cloud : as in cloud computing environment)
english.stackexchange.com/users/14666/Kris
I would use this title for a blog about cloud computing. Which is correct — " on  the cloud" or " in  the cloud"?
"On the cloud" or "in the cloud"?
english.stackexchange.com
<word-choice><prepositions><programming>
english.stackexchange.com/questions/7191
english.stackexchange.com/users/None/
It is not clear that there is a correct answer here and the answer may in fact be subjective. Both "in the cloud" and "on the cloud" are found to be used extensively. The general consensus is that "in the cloud" is the correct form. "On the cloud" could be a good blog title and could mean "relating to the cloud" as well as being on it.  "On the cloud" seems to relate to a specific cloud, and some suggest that context will dictate whether to use "on" "in" or "to". 
It is not clear that there is a correct answer here and the answer may in fact be subjective. Both "in the cloud" and "on the cloud" are found to be used extensively. "In the cloud" seems to be the accepted usage.
This depends on the general meaning that you want to convey. "On the cloud" refers to a specific cloud". "In the cloud" means to say that a resource is part of the cloud, or that you are  in the midst of all the latest happenings in the cloud computing space.  "In the cloud" is where your data is stored, or where your processing takes place, in the cloud computing paradigm. There is no specific right or wrong answer to this question since the answer will depend on what you are trying to convey, and there are many different options.
"In the cloud" is the correct answer. "On the cloud" can be used if writing about a specific cloud. Google offers various results for variations of "on, in" the cloud. The term "cloud" may have orginated from representing the internet as a cloud shape and so "in the cloud" made more sense. "On the cloud" is a nice blog title, where "on" would mean "relating to". There is an understanding the we say the "application" was deployed "on the cloud". But "on" or "in" or "to" will depend on context It will depend on the blog title. But "on the cloud" is a good option both gramatically and technically.
"In the cloud" seems to be the accepted usage.
The answer to this question will depend on what you are trying to convey, and there are many different options. There is no specific right or wrong answer to this question.