Waraji is a simple Java Web Start application that detects class confliction.
It's pretty simple.
Just drag and drop files you want to examine.
Waraji will let you know if there are conflicted classes and their timestamps and file sizes.
Note that Waraji doesn't report confliction under META-INF directory - where the MANIFEST.MF file always exists.
Currently, you need to Relaunch Waraji if you want to examine other jars.