A long-time power-user favorite (especially for travelers whose laptops aren't equipped with 3G/4G), PdaNet has been enabling phone-based tethering since the early days of Android. The app doesn't support Wi-Fi hotspots but instead allows you to share your smartphone's data connection directly with your computer using a wired USB connection.
After installing the app on your phone, you install a companion program on your Windows PC or Mac. You can then utilize your phone's data connection to get your computer online. The one catch: The free version of PdaNet doesn't allow PC-based access to secure (https) websites; in order to access those, you'll have to buy a $16 pro license.