New Products
I pick one of these up every couple of years.
Keeps up with newer powders and projectiles pretty well.
If you want to subscribe to something that's usually a pretty good read, Handloader Magazine is decent: Handloader Magazine: Amazon.com: Magazines
The annual Hodgdon manual in magazine format is a must-buy. Thanks, Vaquero.
As for that link to the Accurate Powders data, all the powder manufacturers used to offer a free manual on paper. They seem to have almost all moved exclusively online at this point.
Alliant - Alliant Powder - Reloader's Guide
Hodgdon, IMR, and Winchester - Hodgdon Reloading | Home
ADI - ADI Powders Handloaders' Guide
That pretty much covers powder manufacturer information sources from the majors who have migrated from paper to online.
There are others reliable sources online. Bullet manufacturers often publish data. For example, from Nosler - Load Data ? Nosler
Some publish wonderful articles that really explain the basics. For example, from Hornady - External Ballistics - Hornady Manufacturing, Inc
If you're willing to accept "manuals" that have been compiled online, there are many, mostly in forum format. This is one of the better known that tries to be more of a manual than a forum: https://www.loaddata.com/home/index.cfm
(ETA: This is usually worth a look: Reloading Pages of M.D. Smith )
Beyond that, you have to start asking yourself how much you trust your sources. Frankly, there's more than enough data online to get you started with handguns. When you get into rifles, there are a few books I'd recommend...but now I'm straying well beyond the original question.
Enjoy yourself. Learning all this stuff is half the fun.