Controlling a Link Sprite camera through an AVR - how to get the data to a PC?
Sometimes for this sort of thing some of the older file transfer protocols such as XMODEM are worth a look. While the speed and error correction aren't as good as many other protocols an advantage is that it's a simple protocol that has a small memory footprint. A search for "AVR xmodem source code" yields quite a few results, for example:

Procyon AVRlib: xmodem.c Source File

On the PC side you can run a terminal emulator program and you'll find many that support XMODEM. Tera Term is one example of a free one that supports it. You'll just need to open the COM port that's been assigned to your USB converter and do a File | Transfer | XMODEM | Receive once your AVR has started the transmission.