The Linux Security Summit for 2011 will be held on the 8th of September in Santa Rosa, CA, USA.
It will be co-located with the Linux Plumbers Conference (LPC).
A full announcement of the event with a CFP will be made later.
If you're interested in attending, subscribe to the Linux Security Summit mailing list:
The list is for general discussion, event updates etc., and will also be used to estimate attendance numbers, so do please subscribe if you are planning to attend.