YAY! Woohoo! I've been accumulating FLV-format files since I figured out how to download them from sites that stream them. But the quality of the standalone FLV players is abysmal. Not one of them does the job without eating up a ton of CPU, and they all software-stretch the image, producing awful blockiness even at 2X. Finally,
Media Player Classic solved this problem for me completely. The video plays as smoothly, is stretched as cleanly, and eats as little CPU as any video format. The site says the last update was over a year ago, but I swear I've downloaded this more recently than that, with no working FLV support. Whether it's my failure to look in the right place or a new development, I'm a happy guy. For some quality test material, try some of the 640x480 vids at ign.com.
Edit:
Internet Download Manager is one tool that will let you grab FLVs after you start streaming them.