CPU Mining
MultiMiner has great support for not just ASIC and GPU mining, but CPU mining as well.
However, in order to take advantage of CPU mining you will need to compile a copy of BFGMiner with CPU mining enabled. While MultiMiner and BFGMiner both support CPU mining, none of the binaries for BFGMiner come with CPU mining enabled as it greatly simplifies using the tools for malware.
You can find instructions for building BFGMiner in its README file. If you are mining on Windows please see these instructions which include details for enabling CPU mining.
You will need to ensure BFGMiner is configured and compiled with --enable-cpumining