What's safe to delete from the HTC SD card?

[RussWWFC]

Hi

I am looking to get rid of some of the stuff on my SD card as there is so much stuff that doesn't need to be on there.

All I really need is the user manual and the maps that are on the device for the HTC Navigation.

I connect to the Mac using it as a disk drive and sync online.

Already replaced the music with my own.

Also can anyone who uses their phone with a Mac let me know if they can synchronise with iCal - I'd imagine you'd have to sync iCal with Google Calendar but just wanted to check

Thanks