Don't rely on everything you have needing photocopier - sometimes it would be easier getting blood from a stone than the code for the photocopier! Sometimes you get to a school too late to be able to use one anyway (gotta love 8.45 am calls). I've got a few lessons I can do with just a story book to start from (I carry a few of these - they're probably the resource I use the most) and paper to write on - means I've got a failsafe to start the day off with while I scrabble resources together for subsequent lessons or play hunt the planning file.
Most bookings I get the work's planned for anyway - very rare I get unplanned days. The things I use more are the time filler type activities - when work's left that they woosh through ("design a poster" I'm looking at YOU) - so it's things like "I'm thinking of a number with X digits, that's even, a multiple of...", elevens, apple pie type stuff, or quick problems on whiteboards, or stuff like that.
I used to take tonnes of resources out with me - I've gradually relegated so many of them to the car boot it's unbelievable. Big things I get a lot of use out of are things like stickers, a puppet (I do mainly KS1/FS), whiteboard pens that actually work (a rarity by about May), whistle for those weeks where you end up in a different school every day and get yard duty/PE every single day and a few good quality storybooks that you can either use for storytime or the starting point for writing - things like character descriptions, alternative endings and the like (I tend to have a couple of KS1 ones and something like a Horrid Henry that I can use for starting points - further up the school you can get upper KS2 kids to write a story for an infant audience and discuss things like patterned predictable text and having pictures to support the story and the like so they even work with Y6 kids in that sense). I've got a netbook with loads of worksheets and IWB files saved on that I can hook up to the IWB projector if I need to (you quite often find that the laptop that powers the whiteboard is off with the member of staff or you can't find a password - but you can usually guess that anyway) but again, it's a very rarely use one.
There's a million threads on the TES supply teachers forums asking similar (if you tend to scroll back to September/August time they tend to pop up around then).
As a heads-up, if you work through multiple agencies you tend to fall into a position of overpaying tax (cos your tax allowance ends up with one agency so anything else gets taxed at full-whack and if you don't get enough work through one agency to use the allowance... if you get what I mean) so it's worth keeping on top of contacting them and asking them to check if you're owed anything - had a great time a few years ago when they just kept finding money they owed me and then had a wonderfully large rebate cheque through the post the other day as well (the taxman's so much nicer when he's giving ME money).
To warn you - it's the worst year I've ever known it for work bookings.