There are a variety of resources available to assist developers with creating Custom Alexa Skills. Here are the ones that I recommend that you check out if you are interested in Alexa Skill Development
GitHub
The Official GitHub Repository for Alexa. Filled with Samples and Information
https://github.com/alexa/
The Official Amazon Alexa Blog – https://twitter.com/alexadevs?lang=en
Many Alexa Evangelists have Twitter Accounts that they update regularly. Here is a list
@theDaveDev
@amit
@JeffBlankenburg
@RobMcCauley
@memodoring
@loisrp
@cwillycs
@Muttonia
@Maxamorde
@mike_maas
@theOnlyAkersh
@sleepydeveloper
@ankitkala99
@Toshimin8
@soganmageshwar
@GlennCameronJr
@PaulCutsinger
Twitch Channel
Amazon maintains a Twitch Channel where various Alexa Evangelists regularly stream coding session for training purposes. These sessions are all free and are recorded for future viewing
You can find the Alexa Twitch Channel at https://www.twitch.tv/amazonalexa
Blogs
The following Blogs provide Alexa Developer with a wealth of information
Amazon Developer Forums – https://forums.developer.amazon.com/spaces/165/alexa.html
Alexa User Voice – direct to product team for requests – https://alexa.uservoice.com