I've just looked at Olimex as a PCB manufacturer and their standard board size is 160x100mm.
I can put multiple Eagle PCBs on one board of this size using cut & paste, being careful with DRC and ratsnest in each individual board file. However, the free version of Eagle is limited by size so I can't actually make use of the whole board area.
Except paying for another version of Eagle, which is out of my price range, is there a way to combine multiple gerber/drill files in order to panellise multiple boards?