The temporary ordination program conducted by Buddhistcc is a very good one. It is carried on at the Dekanduwala meditation centre which is in Horana. It is not a meditation retreat but an over all training in dhamma which runs according to a daily schedule consisting of studies, meditation, and other day to day chores of novice monks.
In fact i went through this program in 2005 and it was one of the happiest periods of my life. They also conduct a one year long tripitaka training program for which also you will have to get ordained.