DNemulator is a package for simulating DNA sequencing errors, polymorphisms, cytosine methylation and bisulfite conversion.
Get the latest version: dnemulator-16.zip
The bisulfite alignment benchmark provides an example of using DNemulator.
Sherman can also simulate bisulfite sequencing experiments. DNemulator can do some things that Sherman cannot, and vice-versa.
MethylCoder includes a BS-Seq Benchmark, using real (not simulated) data. This is obviously more realistic, but it has the disadvantage that the ground truth is unknown.