The two that I consistenly use in my shop are Hornady and Sierra. I'm hoping for the new Sierra manual and software for Christmas.
I also have Nosler, Speer, and Lyman on my shelf, and hyperlinks to
Winchester, IMR powder, Hodgdon powder, and Alliant powder in my Favorites. I've found those to be just as useful, especially while trying to set up for the new 7mm WSM. Not many have load data listed for that caliber yet.
One thing about Sierra, over all the rest. I have yet to have a load out of it that doesn't come out right the first time. Hornady, Speer, and Lyman, I'll usually have to go and tinker with the loads for quite a while until I'm getting the accuracy and velocity I want. Not with Sierra. I will find the "keeper" load during the initial development, if I follow their recommendations for a hunting or an accuracy load in that caliber and bullet weight. I like reloading as well as the next guy...but my patience becomes tested when it takes me 6 months or longer to fine tune a load out of Hornady. Not so with Sierra.
That, along with the excellent advice and customer service at the end of Sierra's 1-800 #, makes it the best manual I have in the shop.
My $.02 worth...
Matt