Necron conversions I've found...

http://santacruzwarhammer.blogspot.com/2011/12/necron-triarch-stalker-conversion.html

that's a triarch stalker conversion I found

http://blog.spikeybits.com/2011/12/new-canoptek-wraith-conversion.html

that's a wraith conversion... he shows you a simpler one on a link through the site

http://blog.spikeybits.com/2011/12/necron-tomb-blade-jetbike-conversion.html

that's for tombblade conversion

spikey bits got others on site and his store sells the bits for the conversions