Not bad: http://lwn.net/Articles/435854/ (may be behind paywall) or http://article.gmane.org/gmane.linux.embedded.celinux.devel/100

From: Constantine Shulyupin
Subject: Fastest ever Boot of Embedded Linux: 300 ms
Newsgroups: gmane.linux.embedded.celinux.devel
Date: 2011-03-28 20:40:42 GMT (3 days, 9 hours and 30 minutes ago)

Hello all,

Make Linux Software presents the fastest ever embedded Linux boot for 720 MHz ARM and NAND flash memory. Linux boot time is 300 milliseconds from boot loader to shell. The first goal of the project is to achieve a minimal boot time of a minimal but functional Linux system on common hardware. The second goal is to provide a platform for developing more
functional systems with an even minimized boot time.

Video of boot process: http://www.youtube.com/watch?v=747XLVbTgA4

Boot log with timestamps:

0.000 0.000: TI X-Loader 1.4.4ss Mar 26 2011 01:45:43
0.000 0.000: Optimised by www.MakeLinux.com
0.000 0.000: Loading
0.237 0.237: Running
0.237 0.000: CFG_LOADADDR=80008000
0.249 0.012: (int)CFG_LOADADDR=e321f0d3
0.276 0.027: Linux version 2.6.32 (const@...)
0.276 0.000: Starting application
0.296 0.020: BusyBox v1.16.2 hush – the humble shell

To learn more, please visit http://www.makelinux.com/emb/fastboot/omap

Thanks.

—
Constantine Shulyupin
http://www.MakeLinux.com/
Embedded Linux Systems,
Device Drivers, TI DaVinci