HTC launch the Windows Phone 7 series and soon will release the jail break for the WP7. I found interesting post and screenshots that claims of getting the "file explorer :) and a VERY nice task manager". That might be a good start for jail breaking WP7.
"I still cannot believe it but I did it... After a good idea, 6 hours of work and a lot a lot of digging I've unlocked the ROM image in the emulator CTP. I will describe tomorrow the method but right now I will just post some screenshots, upload the bin somewhere so I can give you the link and go to sleep cause it's almost 2 o'clock in the morning." - Says Dan Ardelean.
This was in MARCH 19, 2010 (More than 6 months ago) Would be interesting to see the developments and new hacks.
Source : WP7 Emulator "Unlocked"