I have talked before about using JoikuSpot on both my S60 and Maemo devices and it is one of the first apps I recommend you install on your devices. JoikuSpot turns your Nokia device into a WiFi hotspot and while there is a free Lite version, the full Premium version has no closed ports or other limitations. I received an email this morning that you can buy the Premium version for only EUR5 ($6.80) today and tomorrow.
Android 2.2 has this capability integrated into the device and I sure wish Nokia would also do this with the Symbian and MeeGo platforms moving forward. Unlike carrier locked devices though, at least you can easily add this with an inexpensive and effective application.