Is there any method of using iPhone (2G) with Winamp without having iTunes installed?
Are you looking for something like the CopyTrans Manager?
The feature list.
Play iPod tracks directly on any PC
Add music to iPod, videos & more
Organize iPhone or iPod and manage playlists
Remove iPod tracks & playlists
Compatible with all iPod models
This plugin is what your looking for and it has instructions on how it can be done without installing iTunes.
It allows for the management and control of certain iPhone functions from within WinAMP.
However please note the limited support.
Are you willing to consider alternatives to Winamp?
If so, MediaMonkey has iPod (and by extension iPhone) support. The help page starts off with the following:
It goes on to describe how to connect and sync using MediaMonkey so I won't reproduce it here.
It looks like you have to have iTunes installed at some point and there are cases where you need to keep it installed.
This procedure might be worth investigating with Winamp.