When you need to slice a piece of of an MP3 and you don't have time to mess around with downloading a new application and learning how to use it, MP3Cut offers dead simple and web-based MP3 snipping.
Visit MP3cut, upload the MP3 you want to snip — an ideal improvement would be support for URLs that point to MP3 files, but we're not complaining! — and then use the sliders to adjust to where you want to snip the section out of the MP3. You can preview the section which makes it extra easy to get the cut mark right to the millisecond you want. When you've found the section you want to cut out, hit the download button and you're done.
If you have a handy tool to share for sampling sections of MP3s, let's hear about it in the comments. Thanks IveAlwaysGotMail10!