* To build on OSX (32bit)

export CC=/usr/bin/llvm-gcc
export CXX=/usr/bin/llvm-g++
export CFLAGS="-m32 -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.6.sdk -mmacosx-version-min=10.6 -Os -fvisibility=hidden"
export CXXFLAGS="$CFLAGS"

$ ./configure --enable-shared=no

Note that in xcode4 beta builds /Developer would be replaced with /Xcode4

* To build on linux x86:

export CC=/usr/bin/gcc
export CXX=/usr/bin/g++
export CFLAGS="-fvisibility=hidden -m32"
export CXXFLAGS="-fvisibility=hidden -m32"
export LDFLAGS="-static-libgcc" 
./configure --enable-shared=no

* To build on linux x86_64:

export CC=/path/to/gcc
export CXX=/path/to/g++
export CFLAGS=-fvisibility=hidden
export CXXFLAGS=-fvisibility=hidden
export LDFLAGS=-static-libgcc
./configure --with-pic --enable-shared=no

alternatively, just put all those variables on the configure line (note that LIBS is expressed in terms of the path to g++, not the CXX variable):

./configure CC=/path/to/c-compiler CXX=/path/to/c++-compiler [LDFLAGS=-static-libgcc] [-m32] [--with-pic] --enable-shared=no

This will build src/protoc (the compiler binary) and src/.libs/libprotobuf.a (among others).  

publish protoc into src/devtools/bin/<platform>/
publish libprotobuf.a gets into src/lib/<platform>/release