This has been confirmed working! It also fixes some automatic brightness bugs!
It's recommended that you do a nandroid backup before doing this, its a good practice to get in to.
Download these two .img's and flash_image from the following links.

Wifi kernel: boot-new.img

OverClock kernel (thanks to tasmanian_droid) : boot.img

Flash_Image : MEGAUPLOAD - The leading online storage and file delivery service

Place the two .img's in your sdcard root, and flash_image in /system/bin/, which is done by first putting flash_image in your /sdcard, then doing
Code:
adb shell mount -o remount,rw -t yaffs2 /dev/block/mtdblock4 /system
adb shell cat /sdcard/flash_image > /system/bin/flash_image
adb shell chmod 755 /system/bin/flash_image
then boot into recovery mode. From recovery mode, go to mount options and mount both /system and /sdcard, then run from adb

Code:
adb shell /system/bin/flash_image boot /sdcard/bootwifi.img
reboot into Android, run the Wifi tether program(Tether capability with android-wifi-tether (Wireless Tether for Root Users) - Droid Forum - Verizon Droid & the Motorola Droid Forum) once, then reboot back into recovery mode and run
Code:
adb shell /system/bin/flash_image boot /sdcard/boot.img
now reboot your phone into Android, use SetCPU (SetCPU for Root Users [UPDATE 1.4.3a Nexus One] 01/08/2010 - xda-developers or in Market as donate version for $.99) to overclock your CPU to 600MHz, and reboot into recovery mode again, go to mount options and mount both /system and /sdcard, now execute through adb
Code:
adb shell /system/bin/flash_image boot /sdcard/bootwifi.img
reboot again and you have both wifi tethering, a working wifi card, and 600MHz!!

Here is another "do it all" kernel. Download boot.img from Sendspace.com - send big files the easy way Please test this first and post if it works. Thanks to CKyle22