I have a couple of tasks to do with arduino but one of them takes very long time, so I was thinking to use threads to run them simultaneously. I have an Arduino Mega
[Update] Finally after four years I can install FreeRTOS in my arduino mega. Here is a link
In short: NO. But you may give it a shot at: http://www.kwartzlab.ca/2010/09/arduino-multi-threading-librar/