Access files on your Android via Wi-Fi with Samba Filesharing
After you install the app, launch it and create a password -- the default username is SDCARD, though you can change that if you wish. Once your changes have been made, tap your Back button to return to the main screen and then tap Menu to bring up the four action buttons. Disable and re-enable SMB services, and you'll receive a notification with the path to your device -- such as \\192.168.0.100 and \\ANDROID.
You can also configure the NetBIOS name (the ANDROID bit) if you want to use something a bit more personal. The app also features a 'wakelock' which keeps your Droid from dozing when you're trying to access files.
Root access is required, and you'll also need Superuser or Superuser Permissions installed (find one with a quick Market search).
Download Samba Filesharing for Android [AppBrain - QR code after the break]