Here's one way to share files with your android phone over wifi. You can copy files from/to your phone's SD card to/from your Kindle Fire using your WiFi; no cables needed.
A) Both your Kindle Fire and Android Phones are connected to the same WiFi network (Say your home WIFI)
B) ASTRO File Manager in your Kindle Fire and SSHDroid app in your phone
1. Install SSHDroid app in your phone and open it. You'll see IP address of your phone (192.168.??.??) and port (2222?)
1. Install ASTRO File Manager app on your Kindle Fire
2. Open the ASTRO File Manager app in your Kindle Fire and add network by giving the Android phone IP address (and port)
3. You can now use ASTRO File Manager to browse Android Phone contents with your Kindle Fire and copy/paste/delete files
You can also do the other way; connect your Android Phone to access your Kindle Fire.