iPhone 3G: 
http://imodzone.net/download/os4/iphone_os_4_beta__iphone_3g__8a230m.dmg
iPhone 3GS: 
http://imodzone.net/download/os4/iphone_os_4_beta__iphone_3gs__8a230m.dmg
iPod touch 2G: 
http://imodzone.net/download/os4/iphone_os_4_beta__ipod_touch__2nd_generation__8a230m.dmg
iPod touch 3G: 
http://imodzone.net/download/os4/iphone_os_4_beta__ipod_touch__3rd_generation__8a230m.dmg
XCode 3.2.3 and SDK 4 Beta
http://imodzone.net/download/os4/xcode_3.2.3_and_iphone_sdk_4_beta.dmg

tuto windows
http://www.youtube.com/watch?v=h0kRiUGxdnQ&feature=player_embedded