Foreword
First, this is just a way of saying "Thank You" to Linux Mint as the information provided here (at least initially) has been merely copied (from a forum contribution indicated below), pasted, reformatted and a little rephrased by a novice user preferring the great elegance of mintMenu at the expense of just a little loss from speed
Second, this novice LinuxMint user has managed to get the mintMenu working on xfce4 panel but could not solve the puzzle (probably due to the fact these instructions date back to June 2007) presented in item 5 (luckily using Nautilus) and later found a workaround also in the Forum, adding it at the bottom as well...
 

1) Run this in Terminal:

sudo apt-get gnome-main-menu mintmenu xfce4-xfapplet-plugin

2) Right click on the Xfce Panel and select Add New Items...

3) Select Xfapplet and then select mintMenu.

4) Right click on the new mintMenu item and select Move to drag it to where you want.

5) Edit using right-click Preferences. Enter your Preferrences (treat entries following = sign as examples only) under mintMenu --> plugins:

applications:
execute_app = thunar
search_command = catfish SEARCH_STRING --path=/
places:
desktop_cmd = thunar /home/YOURUSERNAME/Desktop
execute_app = thunar
home_cmd = thunar
trash_cmd = thunar trash:///
system-management: 
control_center_cmd = /usr/lib/linuxmint/mintConfig/xfcemintConfig_frontend.py
lock_screen_cmd = xflock4
quit_cmd = xfce4-session-logout
terminal_cmd = xfterm4

EDIT: Thanks to dasunsrule32 @  http://forums.linuxmint.com/viewtopic.php?f=42&t=16937, I can provide an alternative way of implementing the customisations above as follows:
sudo gedit /usr/lib/linuxmint/mintMenu/plugins/system_management.py
(i) Find "gnome-control-center" and replace with "xfce4-settings-manager" (or another alternative like above)
(ii) Find "gnome-session-save --shutdown-dialog" and replace with "xfce4-session-logout" (or another alternative like above)
(iii) And so on...  

6) Now right click on mintMenu and click Reload Plugins.

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Source: LinuxMint Xfce Dev merlwiz79 @ http://forums.linuxmint.com/viewtopic.php?f=143&t=3535