Instead of the normal VACUUM, you can also use VACUUM FULL. However, I really want to point out that VACUUM FULL actually locks the table and rewrites the entire relation. In the case of a small table, this might not be an issue. However, if your tables are large, the table lock can really kill you in minutes! VACUUM FULL blocks upcoming writes and, therefore, some people talking to your database might have the feeling that it is actually down. Hence, a lot of caution is advised.
To get rid of VACUUM FULL, I recommend that you check out pg_squeeze (http://www.cybertec.at/introducing-pg_squeeze-a-postgresql-extension-to-auto-rebuild-bloated-tables/), which can rewrite a table without blocking writes.