I'm looking to use my midi keyboard to trigger musical samples from Reason. I use it for live stuff and I'd like to be able to trigger them while I'm already playing another synth on the program.
Any advice?

You need to get ReCycle... within ReCycle, you can cut a certain section of a wav file into a loop, then add points where you want the song to be broken up... Each of these points will be triggered by a key on your midi keyboard, or midi Pad later...
First things first.. import a wav file into recycle, then you need to add a point where you want the beginning of the sample to be and add a point where you want the end to be... Then right click on each point, and on the left one select "set point as left locater"(may not be exact words but its close to that phrase) then to the same for the end point but "set point to right locator""
Then you need to go to edit "copy loop" ..select that and then once its finished copying, select edit "past loop as new document"
once it opens up in the new document you can turn the "Sensitivity" adjustment up to around 75-85 and recycle will add points for you where it sees fit... then you can re-arrange them and delete them/add more if you want...
After you get all of your points set... go to File>Save As
and name it whatever you want...

Once it's saved.. open up Dr. Rex or NNXT Advanced sampler within reason.. and then load the rex file you saved.. and tada... you have everything chopped up how you wanted it on your keys...

Another advantage of Rex loops is that they an change tempo.

__________________
...