As Matt ("GreenMatt") noted, one of the resources is the Agile CMMI blog.
I am the author of that blog, and I'm also a CMMI appraiser, so, I can provide you with first-hand information on achieving CMMI levels while also incorporating agile practices.
Rob's response is correct, to a degree, but can also be taken the wrong way. Your processes must be known to you, which is more important (and different) from being "documented". You need to plan your processes so that you can manage them at maturity level 2. Also, your processes would need to be conducted in such a way that they are able to achieve certain goals that are listed in CMMI.
For Maturity Level 2 and Scrum, what's important is that you are truly following Scrum and are not leaving out the hard parts like: calculating velocity & using velocity to set sprint backlogs, setting sprint goals, and not disrupting the sprint in the middle, etc.
As Rob correctly pointed out, CMMI contains no processes. What CMMI does have are only practices to improve your processes. That means you do need to know your process in the first place or CMMI will only confuse matters.
Matt is right, it's not the CMMI makes things hard, it's just that poor uses of CMMI makes things hard. And, he's also correct that ML2 has little to do with the actual development and much more to do with running the project and managing scope. The bottom line is that CMMI and Scrum at ML2 is very easy together, as long as you are clear about how you're using both.
These are some of the tips I can easily provide in a forum like this. Feel free to look me up and get in touch for a more detailed conversation.