Currently I am using Samsung Galaxy 3 (i5801) with Android 2.1. Is there any app available to support flash video ?
There is an alternative browser, Skyfire, which purports to support at least some Flash videos on Android 2.1.
It should be available in the Market.
assuming you're in the united states it's just a matter of days before you get your 2.2 update which comes with Flash. I don't believe any other aftermarket player will decode FLV files for you at this time.
you can install flash by these steps
The first step is to download flash_for_21.zip to your computer and extract the .apk file.
Now navigate to the market and install “Apps Installer” utility to your phone. Now connect your Android phone to the computer and copy .apk file to your SD card. Make sure that it is in SD card root and not in a sub folder. After this launch “Apps Installer” on your phone and follow the on screen instructions to install flash_for_21.apk file. After installation is complete, simply reboot your phone and there you go! You now have Flash 10.1 on your phone.