You can now root without rsd lite using adb. The adb method is easier and has less room for error so I would suggest using it. Click me for the thread

9/9/2010 I strongly suggest using the method linked above instead of the one in this thread. In a few days I will no longer have a Droid which will make supporting this thread much more difficult.

This will also work for going from stock 2.1 to Rooted 2.2

I do not know of a way to flash sbf files on a mac. To use this guide you will need either a Windows or Linux computer

The Linux method has been redone today(8/23) and is a much better method with lss chance of issues arising. If you have access to a Linux computer I would strongly suggest it over using windows.

How to Root 2.2 from Windows

Wiping data is not required

Please read the entire guide and before starting the process.

Windows Instructions: 

1.) Download 2.1 SP Recovery sbf to your C: root directory (C:\)

2.) Download md5sum 

3.) Place md5sum in c:\windows\system32

4.) Download in install RSDLite 4.6 for this file you may need an un-zip tool like WIN RAR

5.) Download and install the correct motorola drivers for your windows machine (32 for XP, 32 or 64 for Vista depending on Vista version)

Current Motorola Drivers

6.) Run command prompt (Start->Run then type "cmd" and hit enter)

7.) Change directories to your C:\ root directory (cd c:\)

8.) Type in "md5sum SPRecovery_ESE81.sbf"

9) Make sure the sum of the image is EXACTLY 9b6a336cd8f067d4487935468c758d89

10.) Connect phone via USB and reboot, while rebooting hold UP on the dpad

11.) Run RSD Lite 4.6

Windows 7 64 Bit Users See Hidden Instructions

1. Navigate to the install folder which is usually C:\Program Files\Motorola\RSD Lite
2. Right click on SDL.exe
3. Click run as administrator

Also this post here has great info on getting rsd lite to work

12.) Select the SPRecovery 2.1 SBF file
13.) Click Start and wait for RSD Lite to flash the SPRecovery image onto phone and then wait on phone to reboot.
16.) Your phone will boot now boot up and tell you that your battery is dead. Just pull the battery out.
17.) Put the battery back in and hold X while powering on your droid.
18.) Download a rom check the roms forum for roms. If you use one of the following roms you can skip steps 24 and 25 FRG01B FRG22D thanks to Pete
19.) Back on the phone go to mount options. (Note you can use the volume rocker to navigate and the camera button to select.)
20. Then press Enable USB Mass storage
21.) Place the file in the root of your sdcard.(Not in any folder just on the sd card.)
22.) Rename the rom to update.zip. Be sure that you are only naming it update.zip. Windows often does not show file extensions and you will end up with files named update.zip.zip.
23.) Then Disable USB Mass Storage
24.) Wipe data/factory reset
25.) Wipe Cache Partition
26.) Click on install
27.) Press allow update.zip Installation
28.) Press Install /sdcard/update.zip (deprecated)
29.) When the install is complete use the power button to go back to the main menu
30.) Reboot

How to Root 2.2 from Linux

Wiping data is not required

Step Numbers highlighted in blue should be done on the computer, step numbers highlighted in pink should be preformed on the phone and step numbers in yellow involve both the computer and the phone.

Please read the entire guide and before starting the process.
Linux Instructions (Please note I have Ubuntu 10.04 this should work on other Linux distros but I have not tested it.)
1.) Download 2.1 SP Recovery sbf 
2.) Go here and download sbf_flash
3.) Download this update.zip and place it in the root of your sdcard(Not in any folder just on the sdcard).
4.) Run Terminal and cd to the directory with sbf_flash and the .sbf file
5.) Type in md5sum SPRecovery_ESE81.sbf
6.) Make sure the sum of the image is EXACTLY 9b6a336cd8f067d4487935468c758d89
7.) Connect phone via USB and reboot, while rebooting hold UP on the dpad
8.) In Terminal type “chmod +x sbf_flash” no quotes
9.) Now type sudo ./sbf_flash -r --recovery SPRecovery_ESE81.sbf 
10.) Most likely you will be asked for your Linux password. So enter it.
11.) Your phone will be rebooted into the bootloader.Turn off the phone unplug it.
12.) Power on your phone while holding the x button. This will get you into SPRecovery. If your phone boots up without getting into SPRecovery you will have to start the process over again.
21.) Click on install (Note you can use the volume rocker to scroll and the camera button to select.)
22.) Press allow update.zip Installation
23.) Press Install /sdcard/update.zip (deprecated)
24.) When the install is complete use the power button to go back to the main menu
25.) Reboot

When it boots back up you will have stock froyo with root

Unfortunately the custom recovery will not stick at this point, you recovery will revert to stock. See this thread for a solution