Try Atomikos TransactionsEssentials.
Atomikos is the inventor of "Java EE without Application Server", so if any open source JTA/XA does well in Java SE then it must be TransactionsEssentials: it was designed for Java SE right from the start, and includes JDBC and JMS connectors/pools so you don't need any application server functionality.
Because of its Java SE focus, TransactionsEssentials also has very few dependencies on third-party jars or platforms.
Best
Guy
Disclaimer: I work for Atomikos, but still...
