If you want to download the kernel with Ubuntu patches, you can either download the source package of one of the binary kernels:
Originally Posted by k210in
which downloads and decompresses the source of the 'linux-image-2.6.32-24-generic' package, or you can install the 'linux-source' package:
apt-get source linux-image-2.6.32-24-generic
which drops a tarball of the kernel in /usr/src.
sudo apt-get install linux-source
You might also need all the build dependencies for the Linux image:
sudo apt-get build-dep linux-image-2.6.32-24-generic