I had the need the reboot my Linksys WRT54G router remotely. Unfortunately, the web interface is not like DD-WRT where a reboot button is available; however, there IS a hidden page.
1. Login into the web admin page, which is by default: http://192.168.1.1.
2. Add reset.htm, as in http://192.168.1.1/reset.htm.
3. Click “Yes” to reboot.
Another method is to back up your config, the restore it — but do this with caution!