Ever since they cut off our internet access at work, I've been using the Tether application and it works great! It's been invaluable to me to take care of my businesses from my laptop during the work day. You won't find blazing speeds, but they continue to work to improve both the product and the speed and are very receptive to ideas you might have to improve the product.
They recently released a bluetooth version of Tether which is great. Had some minor issues getting it to work with Windows 7, but Tether responded with an improved product which now displays a list of bluetooth devices within range and allows you to pick one from the dropdown. Still a few minor kinks to work out with this version, but overall, it's a great product that I rely on every day!