There are many powder choices, depending on what you are trying to accomplish.
Unique would possibly be a powder to look into the loading tables for.
It's been around a long time, and is very flexible (hence the name).
It is the original 45 colt powder, and works well in 44 special as well.
Once you figure out what you want to do with your loads, there are other choices, but Unique would be a good powder to play with to start things off.
A reliable source of loading data is mandatory. The Alliant web site is a good and free place to start.
http://www.alliantpowder.com/reloaders/default.aspxLike Delmonico said, get a couple of good manuals and read them cover to cover. You can't have enough information. Always check multiple sources as a sanity check. If two sources disagree by a little, well, that can happen. If they disagree by a lot, one of them is probably wrong. Typos still happen. Always check at last two sources.
Rick