eventmachine
# yum install gcc-c++

mechanize
# yum install libxml2-devel
# yum install libxslt-devel

mysql
# yum install mysql-devel

swiftiply
mapper.o error
(a) modify
/usr/local/lib/ruby/gems/1.8/gems/swiftiply-0.6.1.1/ext/fastfilerader/mapper.cpp
(b) add header
#include <cstring>
#include "unistd.h"
(c) Run "setup.rb"
/usr/local/lib/ruby/gems/1.8/gems/swiftiply-0.6.1.1/ruby setup.rb