This works better than the method by headtailgrep at http://www.pdastreet.com/forums/showthread.php?s=&threadid=47229 because Blackberry Desktop will auto-uninstall headtailgrep's installs, but not Blackberry Desktop's installs.  htg's method works for generic Java applications, while this method works for Blackberry applications.

This method is useful if you don't have a Blackberry data plan.

EDIT: Please note that you do have to have a data plan, just not a "Blackberry data plan."

Prerequisites:

1. Firefox (could use another browser if it lets you change your user agent)
2. User Agent Switcher 0.6.11 add on for Firefox (or your browser's equivalent). See http://chrispederick.com/work/user-agent-switcher/
3. BlackBerry Desktop Software (I'm using 4.6.0.12)

Actions:

1. Define a user agent:
   1. Description = blackberry 8700
   2. User Agent = BlackBerry8700/4.1.0 Profile/MIDP-2.0 Configuration/CLDC-1.1 VendorID/180
2. Set Firefox to use this user agent.  Check to make sure it did via Tools/User Agent Switcher
3. Browse to m.google.com
   1. Click on Gmail
   2. Click on Install Now.  This will download http://m.google.com/app/v2.0.5/L1/BlackBerry-41/GoogleMail.jad
   3. Save it as C:\temp\bb\GoogleMail.jad
4. Edit C:\temp\bb\GoogleMail.jad with a text editor that can handle newline-terminated lines
   1. Find all lines containing RIM-COD-URL.  In GoogleMail.jad, there are 4, named:
      1. GoogleMail.cod
      2. GoogleMail-1.cod
      3. GoogleMail-2.cod
      4. GoogleMail-3.cod
   2. Using the path (not the file name) from the .jad file url (e.g. http://m.google.com/app/v2.0.5/L1/BlackBerry-41/) construct the .cod urls:
      1. http://m.google.com/app/v2.0.5/L1/BlackBerry-41/GoogleMail.cod
      2. http://m.google.com/app/v2.0.5/L1/BlackBerry-41/GoogleMail-1.cod
      3. http://m.google.com/app/v2.0.5/L1/BlackBerry-41/GoogleMail-2.cod
      4. http://m.google.com/app/v2.0.5/L1/BlackBerry-41/GoogleMail-3.cod
5. Download the .cod files into C:\temp\bb
6. Create a file that looks a lot like this, and name it C:\temp\bb\GoogleMail.alx.  (Lines must be CR/LF terminated.):

<loader version="1.0">
<application id="Gmail:Google">
<name>Gmail</name>
<description></description>
<version>2.0.5</version>
<vendor>Google</vendor>
<copyright></copyright>
<fileset Java="1.0">
<files>
GoogleMail-3.cod
GoogleMail-2.cod
GoogleMail-1.cod
GoogleMail.cod
</files>
</fileset>
</application>
</loader>

 Note: It is important to take the value for VERSION from the MIDlet-Version row in the .JAD file.  Otherwise, BB desktop can tell you "No additional applications designed for your device were found"  Other reasons for this message include:

• You need to download the software that tells the Desktop Manager how to properly talk to your device.

  RIM calls this software the “Device” software (or "BlackBerry Handheld Software" for newer versions), but it is your PC's device driver for the BB.

  To see the version of the device software you have installed, Desktop Manager/Help/About/Device_Software”.  If you don’t see your BlackBerry model in the list, Download it from http://na.blackberry.com/eng/support/downloads/download_sites.jsp  .

  Select your carrier and then select the software for your model.   (I used BlackBerry Handheld Software v4.2.1.155 (Multilanguage).)

• Check to see if your file is exactly like mine.
• You need CR/LF terminated lines (I think).
• Don't put a trailing CR/LF after the last line

7. Open Blackberry Desktop
   1. Application Loader
   2. Add-Remove applications
   3. Browse to C:\temp\bb\GoogleMail.alx