Hello,
I am aware that this question is not directly FreeRTOS related and might lack details..
I'd appreciate your input.

Using STM32F4* device I'd to achieve the following tasks:
File management (on SDCard)
FTP server
TCP/IP maintenance port (we’ll define the protocol, custom application)
USB, Mass storage device (SDCard)
CAN and Audio recording (to SDCard)

*All tasks are low priority, there isn't any demanding task.

Are there libs (free/commercial) that will help me with those tasks?
Do you know if there is another RTOS that (free/commercial) that will incorporate those elements?

Thanks,
Ariel.

You can put that together using free software. For example, go to the eval board for the STM32F4* on the ST website and download the demonstration builder firmware and you will find a lot of (but not all of) what you want already running on FreeRTOS.

Go to http://www.st.com/internet/evalboard/product/252217.jsp select the Design Support tab, and then scroll down to the Firmware section.

If you want something put together for you using commercial supported parts then contact the OpenRTOS folks.

Regards.