Normally I carry my XT, my 10-20mm, my 30mm 1.4 and use my 28-135IS as my walkaround. If its night time I carry my tripod or monopod.
This year will be fun as it will be the first with my 70-200mm F4L and my flash unit so I'll probably abandon the 28-135IS in favour of these. Oh and I bought an S5IS as backup (and my wife can use it)
Cheers
JC