Firmware for the WL-500g can be found here: ftp://www.asus.com/pub/ASUS/wireless..._WL500g_en.zip
Changelog: (OFFICIAL confirmed by Asus)
1. Add: Tx Power adjustment.(Only for power user)
2. Add: "Tx Only" for Idle Disconnect Time of PPPoE in seconds
3. Add: PPPoE connection status in detail
4. Add: "Protocol Number" in Virtual Server(for example GRE, OTHER 47, for PPTP server in LAN)
5. Add: DHCP Server that allows fixed MAC address
6. Add: "ZoneEdit" for DDNS
7. Add: WAN Status report when wan connection is disconnected
8. Add: Redirect to Quick Setup when first time access
9. Add: Allow Filter rules into DMZ(ok)
10. Add: Enable NAT Firewall when Internet Firewall is enabled.
11. Fix: DDNS bug when dhcp release/renew is performed.(DDNS abuse)
12. Fix: Printer support for HP1210 psc
13. Fix: PPTP server behind WL500g/b passthrough
--- UPDATE ---
Oleg discovered that it seems there was an error in the firmware, some users using PPTP could not connect anymore
NON OFFICIAL fixed firmware can be downloaded here:
http://files.wl500g.info/asus/wl500g...0g_en_pptp.zip
USE THIS FIRMWARE AT YOUR OWN RISK!