Sampled drum loops, or breaks, have been a mainstay of electronic music production for years, first emerging in hip hop before making their way into early house, breakbeat, drum & bass, etc. The term "break" comes from the source of these samples: the instrumental break in old funk and soul records (typically the part where everything but the drums drops out.)
Unprocessed breaks can be a great way to add an "organic" feel to your songs, however, this usually entails building your track around the break. Why not put them to work for you and make them fit whatever idea or genre you're working on? A few examples of things you can do with drum breaks:
re-pitch or warp them to change the tempo
warp them to change the groove
slice them and re-arrange them to create an entirely new beat
layer single-hit samples to add more energy (kick, snare, etc.)
These are all fairly common techniques in electronic music production, especially drum & bass, but can seem daunting if you don't have a good work-flow.
Give me a break
First, an obligatory word on legality: if your song contains samples from copy-written material you will need permission from the copyright holders in order to release it. That said, there is a definite grey-area surrounding the legality of sampling, especially for short samples, and more so when they're processed and mangled beyond recognition. But just be aware that you might be breaking the law if you don't clear your samples.
With that out of the way, Google is a pretty easy way to find breaks. Just try searching for some classics by name and you'll stumble upon sites with many more: Action, Hot Pants, Amen, Apache, Funky Drummer.
Alternatively, if you want something unique or you have concerns about the legality, you can find modern sample CDs of royalty-free drum recordings. I've found these typically lack the character of the classics, but no doubt there are some good ones out there if you spend the time looking.
First thing's first
If you want to follow along I've prepared an Ableton Live 9 set showing each step I'm describing in this post.
Let's start by dragging a break into a new audio track and preparing it for slicing. I'm using the "Sandman" break. The timing on this break is pretty tight so I don't need to do much to clean it up. I'm just going to warp it (straight), set my start and end markers, and set the Warp Mode to "Repitch". If it were a longer break there might be a bit of drifting in the tempo which would require me to add additional warp points.
I'm choosing "Repitch" mode because I want Live to change the pitch of the audio to fit my tempo (174 BPM, in this case). "Beats" mode would also work, but because I'm changing the pitch so drastically (the break is ~119 BPM), each slice wouldn't actually have time to complete before the next one begins.
Next I'm going to consolidate my warped clip (Right-click -> Consolidate). This is to ensure that, in the next step, Live is using the processed audio to create the slices.
Here you can hear the original break unwarped, and then warped with Repitch mode:
Slicing and dicing
Time to slice. Right-click the consolidated audio clip and choose "Slice to new MIDI track". You have a couple options here in terms of how the audio is sliced. Firstly, you can specify how Live identifies each slice (by transient, or by note length). I generally select Transient. Secondly, you can choose a preset for the Drum Rack that will be created. The "Built-in" modes do the least amount of processing, so these are generally my preference.
Now I'm going to edit the MIDI by doubling the clip length and adding a few ghost notes:
I've also quantized the clip and applied an MPC 16 Swing groove from the Groove Library.
The last thing I'm going to do is roll off the low on the break, since I'll be layering a kick and I don't want my kick to fight with the low-end in the original break.