Here is some FREE resources to enrich your knowledge in computer world
Packtpub Publishing giving you free their ebook daily, you can check here : https://www.packtpub.com/packt/offers/free-learning
Syncfusion giving you 75+ title free ebook, you can check here: http://www.syncfusion.com/resources/techportal/ebooks, the good point in this section is, Syncfusion release ebook for many topics, not only in programming world, also in Mathematics and Excel
Telerik Whitepaper, http://www.telerik.com/whitepapers, some contains tutorial from Telerik component, but it worth to download and read it
DZone refcardz https://dzone.com/refcardz, contains biggest cheat sheets that helps you
If you have another resources, please share with us in the comment section.