Condition 1: Find a FLV converter that can convert FLV file to other video formats:

FLV to AVI MPEG WMV 3GP MP4 iPod Converter is a powerful FLV decoder which can convert FLV files to Almost all other video formats with fast speed and hight output Quality.This FLV converter is a professinal tool to convert FLV video to regular video and audio files, including FLV to AVI, MPEG, WMV, DivX, Xvid, ASF, 3GP, MP4, iPod, PSP, Zune and MP3, WMA and WAV audio formats. here is the free download link:

FLV to AVI MPEG WMV 3GP MP4 iPod Converter

Condition 2: Find a FLV converter that can batch convert other video formats to FLV video foramts:

Allok FLV converter is infact a FLV decoder which can converter other Video formats, e.g.DivX, XviD, AVI, WMV, MPG, MPEG, MP4, M4V, FLV, 3GP, ASF, RM, RMVB, MOV, ASX, MKV, OGM, SVCD, VCD, VOB to FLV video formats. This FLV converter is stable with fast converting speed. So if you want to convert other videos to FLV file formats, I recommend this FLV file converter.Me too, I also often use it to convert other videos to flv files as I have a video website of myself, we also know that youtube also use FLV formats to store videos.Here is Allok FLV converter free download link :

Allok FLV converter

Note: Some guys may want to find a FLV converter which can directly convert DVD to FLV video. I suggest Xilisoft DVD RIPPER Platinum or Imtoo DVD Ripper Platinum, you can directly Rip DVD to FLV video formats. It is easy to use, here is the free download link:

Xilisoft DVD RIPPER Platinum

Imtoo DVD Ripper Platinum

Condition 3: Want to find such a FLV converter that can directly Convert Youtube FLV videos online to other popular Video formats .
We temparlly Call it Youtube Online FLV converter. Here I suggest Xilisoft Online Youtube FLV converter and Imtoo Online Youtube FLV converter
This two Youtube FLV online Converter also is Youtube donwloader. you can use either one to download FLV videos form Youtube.com and convert FLV videos to video formats. With its "downloading + converting" one-step solution, you can easily save FLV videos from YouTube to play on your iPod, PSP, mobile phone, Apple TV, Zune, iPhone etc. directly.and FLV to AVI, MPEG, MP4, 3GP, H.264/MPEG-4 AVC, PSP MPEG-4, ASF, FLV, SWF, etc. Here is the download Link:

Xilisoft Youtube Online FLV Converter

Imtoo Youtube Online FLV Converter

Ofcource you can also download FLV files from website(such as Youtube.com)(Note: How to save FLV file from youtube, pls see the guide: How to download youtube video and save video youtube on your computer), and then use
FLV to AVI MPEG WMV 3GP MP4 iPod Converter to convert FLV files.(see Condition 2)