I prefer
CDex, as it does an excellent job with everything you throw at it, and is fairly simple to use (needs a bit of configuration to get started, but that's easy). I'd generally recommend you use the LAME plugin for encoding, and stick to the -alt-preset-standard setting. It encodes to mp3 format, and that particular preset contains a number of tweaks to ensure you get excellent quality while keeping the filesize relatively small. Stay away from Windows Media Player if at all possible. It'll rip to WMA format, which can be difficult to play in some portable players or on some systems.