PicoHttpD -- tiny library for easy creation of standrad compliant HTTP servers in C++. It is just HTTP/1.1, abstracted from communications and task handling - pure essence.
It is C++ port of httpd part of pthrlib - nice C package by Richard W. M. Jones.
AndreWS is a tiny embedded Web Server writtend in C++ primarily for easy creation web interfaces with Google Web Toolkit for systems written in C++. AndreWS has very flexible, true object oriented architecture that makes it easy to use and extend.