Call it the Great Twitter Paradox: The wildly popular, supersimple microblogging service barely has any features at all--yet it's remarkably rich, thanks to an array of third-party applications and services that make it more convenient, more powerful, and more enjoyable. Here are ten handy tools (plus one bonus) for Twitter novices and diehards alike, including some of my personal favorites and several that got hearty recommendations when I asked my 4900 Twitter pals for nominations. Want more? The Twitter Fan Wiki lists hundreds of Twitter-enhancers, from Twanslate (language translation via Twitter) to Tweetwhatyoueat (a Twitter-based food diary).
And if you're looking for additional PC World coverage of Twitter, check out "8 Ways Twitter Will Change Your Life," "Twitter Hack: How It Happened and What's Being Done," and "Connect to Customers With Twitter."