I have found a great YouTube video, how can I play it on iPhone? This PPT can tell you how to convert Youtube .flv to mov(iPhone supports) on mac free with Adoreshare Video to iMovie Converter. This is a pro video converter, it supports all formats and can customize the video , Just several seconds, you can get the converted video, and then you can syc the video to your iPhone

1. How to convert YouTube .FLV
to .MOV on Mac free?
Support by Adoreshare.com

2. Sometimes you have a flv video or download some FLV videos
from video-sharing website like YouTube, MySpace, Google Video,
Yahoo Video etc, you may want to play them on QuickTime offline,
or edit them in iMovie, Final Cut Pro. What should you do?
The best way is convert .FLV files to .MOV, this PPT can tell you
how to do

3. MPEG-4 (.mp4)
MPEG-4 Part 14 or MP4, a digital multimedia format used
to store video, audio, subtitles, and images. It is the best
video format for iMovie if you want a smaller video file
size.
QuickTime Movie
(.mov)
This file format specifies a multimedia container file
containing one or more tracks, each of which stores data
like audio, video, effects or text.
MPEG-2
aka H.222/H.262 as defined by the ITU, it is the core of
most digital television and DVD formats.
AVCHD
Short for Advanced Video Coding High Definition, it is a
file-based format for the digital recording and playback of
high-definition video.
DV & HDV
This format is for storing digital video recorded by
camcorder. If you want video for better quality, it will be
the best format for iMovie as it is uncompressed.
1. Video Formats Supported on iMovie
Video Formats Supported on iMovie

4. Adoreshare Video to iMovie Converter for
Mac is a utility that lets you convert video files
you can import them into iMovie when:
 You can't import videos in FLV, WMV, AVI
formats to iMovie that it doesn't support.
 QuickTime movies encoded with codes that
iMovie can't recognize.
 MP4 videos recorded from some camcorders
won't be imported to iMovie.
 iMovie won't accept MPEG files that are muxed
(multiplexed) MPEG-1 or MPEG-2 videos.

5. How to convert?
Import Setting Convert
The whole conversion Process

6. How to convert?
Step 1: Download Adoreshare Video iMovie Converter for Mac
and install it

7. How to convert?
Step 2:Import YouTube files. After you launch this
software, click Add button to import videos for conversion.

8. How to convert?
Step 3: Select iMovie as the target to transfer to. It is
located in the Video category
Click Convert button to convert YouTube FLV to iMovie

9. DownloadYouTube Tips
 At first, ensure your Mac is Internet-connected.
 Open browser type “en.savefrom.net”
 (no quotation marks) and hit Enter key to get into the webpage.

10. Related Reading
1 How to Convert MOV Videos to AVI on Mac
Top 10 Free Software and Online Programs
2 to download any Video any Website