Leica is offering mail-in rebates on  selected M-Lenses (May 1 till June 30, 2009):
$5,000 and more and get $500 back (mail-in rebate)
$4,000 to $4,999 and get $400 back (mail-in rebate)
$3,000 to $3,999 and get $300 back (mail-in rebate)
$1,000 to $2,999 and get $200 back (mail-in rebate)
(Source)
Leica M8 upgrade rebates:
Leica Camera Inc. will offer customers who buy [...]
… extra free battery and complimentary Leica leather memory card wallet. I was not sure if Leica US will honor all 3 rebates at the same time, but it was no problem. In addition, since I purchased it from my local authorized dealer on a Leica Demo Day, I did not have to pay any taxes (well, Leica [...]
For a limited period and at participating authorized UK Leica dealers only you can benefit from 15% off the SRP of a range of M lenses.
Full conditions of the offer are outlined below:
To qualify to receive a Leica cash back reward of 15% of the VAT inclusive purchase price paid (up to the Leica SRP), [...]
B&H already has the Leica rebates available on their web site:
Leica M8
Leica D-Lux 4
Leica C-Lux 3
Leica 50mm f/1.4 Summilux M
Leica 50mm f/1.0 Noctilux M
Full list of Leica M lenses eligeble for rebate*
*The following lenses are excluded from the promotion: 50mm/f0.95, 21mm/f1.4, 24mm/f1.4 & 24mm/f3.8.