Take a look at DroidFu, and in particular the DroidFu HTTP components. They're a fairly thin wrapper around the Apache Commons HTTP stuff, but they fit most needs pretty well. It includes some niceties like optional HTTP and model caching, and even "why isn't this built in to the platform" stuff like GZip. (An aside: android.net.AndroidHttPClient is a pretty good upgrade to the older stock DefaultHttpClient stuff when you need to drop down for a little more control, but it's Android 2.2+ only and is fairly underdocumented).
If you just need multipart with a minimum hassle, you can try android_multipart_post, though I've never tried it.
EDIT:
DroidFu is now discontinued. These days if I was starting a new project I'd almost certainly use Volley, with OKHttp if I needed more control (you can even use OKHttp as the transport layer for volley if you want to do both).
