Rome - Alternative Places To Visit

[shivvy]

Following on from March-Hares question about Rome, I'm looking for opinions and suggestions for less well known things to do or places to see.
Any suggestions for museums would be good and I'd also be interested in any day trips to places outside Rome.

Thanks.

[Buenchico]

I'll just add to my recommendation of Ostia (in MH's thread) by pointing out that it makes a very pleasant day out in itself because you get to see the wonderful Ostia Antica site and then head just down the train line to Lido di Ostia to enjoy the seaside.

The train line to Ostia is included in 'Metrebus' tickets:
http://europeforvisitors.com/rome/transportation/rome-metrebus-tickets-and-fares.htm

The Telegraph has lots more suggestions:
http://www.telegraph.co.uk/travel/destinations/europe/italy/rome/10606648/Rome-guide-lesser-known-attractions-bars-and-restaurants.html