With this module you can split any menu block into two different blocks: a first block with the first level menu entries only and a second block with any second level and sub level menu entries. You can have as many splitted blocks as you need.
Version 5.x-2.x uses menu entries of any type, so you can actually use any menu entry created by you or by any other module.
This is a very simple module I needed for a project. If you need something more configurable I would recommend you to use the Menu block module.