One of the best places to start is with some great books. Here are my recommendations:
- HTML5 Guidelines for Web Developers
- Introducing HTML5 by Bruce Lawson and Remy Sharp
If you are also going to use .NET, I would recommend you skip vanilla ASP.NET and go straight to ASP.NET MVC. It will save you two learning curves. With MVC, you go forego learning web services as you can use MVC controllers as in RESTful way. I've been using MVC since the GU announced it in Dec of 2007 and have yet found a reason to use a web service anymore.
The learning curve is not really that steep, but it can seem that way. Just carve out a little time each day to learn a new piece. Kendo UI will really help you with a lot of it and help reduce some of the learning curve.