I'd like to know how to create a system tray popup message with python. I have seen those in lots of softaware, but yet difficult to find resources to do it easily with any language. Anyone knows some library for doing this in Python?

With the help of the pywin32 library you can use the following example code I found here:

from win32api import *
from win32gui import *
import win32con
import sys, os
import struct
import time

class WindowsBalloonTip:
    def __init__(self, title, msg):
        message_map = {
                win32con.WM_DESTROY: self.OnDestroy,
        }
        # Register the Window class.
        wc = WNDCLASS()
        hinst = wc.hInstance = GetModuleHandle(None)
        wc.lpszClassName = "PythonTaskbar"
        wc.lpfnWndProc = message_map # could also specify a wndproc.
        classAtom = RegisterClass(wc)
        # Create the Window.
        style = win32con.WS_OVERLAPPED | win32con.WS_SYSMENU
        self.hwnd = CreateWindow( classAtom, "Taskbar", style, \
                0, 0, win32con.CW_USEDEFAULT, win32con.CW_USEDEFAULT, \
                0, 0, hinst, None)
        UpdateWindow(self.hwnd)
        iconPathName = os.path.abspath(os.path.join( sys.path[0], "balloontip.ico" ))
        icon_flags = win32con.LR_LOADFROMFILE | win32con.LR_DEFAULTSIZE
        try:
           hicon = LoadImage(hinst, iconPathName, \
                    win32con.IMAGE_ICON, 0, 0, icon_flags)
        except:
          hicon = LoadIcon(0, win32con.IDI_APPLICATION)
        flags = NIF_ICON | NIF_MESSAGE | NIF_TIP
        nid = (self.hwnd, 0, flags, win32con.WM_USER+20, hicon, "tooltip")
        Shell_NotifyIcon(NIM_ADD, nid)
        Shell_NotifyIcon(NIM_MODIFY, \
                         (self.hwnd, 0, NIF_INFO, win32con.WM_USER+20,\
                          hicon, "Balloon  tooltip",msg,200,title))
        # self.show_balloon(title, msg)
        time.sleep(10)
        DestroyWindow(self.hwnd)
    def OnDestroy(self, hwnd, msg, wparam, lparam):
        nid = (self.hwnd, 0)
        Shell_NotifyIcon(NIM_DELETE, nid)
        PostQuitMessage(0) # Terminate the app.

def balloon_tip(title, msg):
    w=WindowsBalloonTip(title, msg)

if __name__ == '__main__':
    balloon_tip("Title for popup", "This is the popup's message")