RTA route 1 now connects to the Metrolink station on weekends. They ought to have been doing this 5 years ago, and it's still a little ways from perfect... but at least they're doing it now, right?
Connections on the Saturday Eastbound bus available to IEOC trains 857, 859, 860 and 861, San Bernardino trains 351 and 357, and Amtrak California bus 5415.
Connections on the Saturday Westbound bus available to IEOC trains 860 and 861, and Amtrak California bus 5417.
Connections on the Sunday Eastbound bus available to IEOC trains 857, 858 and 859, San Bernardino train 365, and Amtrak California buses 5415, 5417 and 5403.
Connections on the Sunday Westbound bus available to IEOC trains 858 and 860.
Note that train 860 on Saturdays becomes 377 with service to Los Angeles via San Bernardino, and 858 becomes 375 with similar service.