How to keep rabbits happy

Before Christmas at college we were learning about enrichment and toys and things to stop animals becoming bored, and when I was cleaning out the rabbits later in the day I saw some of the things they had in their aviaries. They had a tennis ball on a bit of rope, hanging from the roof with a hole cut out of it. I assume this is safe for them, but my rabbits would probably chew it all to bits quite quickly so I just wanted to check here.
What else can I give them? I know they can have cardboard tubes filled with grass and vegetables. They have some pet shop toys, but they've had them a long time. I was going to buy a treat game for them so they have to get their food out of different parts of the game, rather than just have it in a bowl. When I get my rabbits new toys should I swap them round so they don't always have the same toys?

Cardboard boxes!!! Haha.

It's the only thing my lot go absolutely nuts for! That, and willow balls

You can never have a bored bun when cardboard boxes are about! :lol:

i know it sounds silly but when getting your buns toys try and 'think' like them. i love getting them toys and i have wasted money on things i think are cool and they couldnt care less. bella is a chewer and likes to throw things around so cat jingly balls and wood chews are fab for her. jasper likes to destry anything so i make him toys filled with treats

A digging box filled with soil, compost or play sand.

Thank you, I'll see if the rabbits like them. I gave them a paper bag a few weeks ago but as soon as Archie stood on it and it made a noise Izzy got scared and ran away :lol:
My rabbits both like food, so I was thinking about getting them this:
http://www.deemillen.co.uk/product_info.php?cPath=219_224&products_id=1169

I'm also going to try and add another chair or something in their run to give them another level to jump on.

I hide my buns pellets in a treat ball then hide the treat ball but my they are just getting quicker and quicker at getting it.

So Dad has suggested something like this but at ground level:

http://www.youtube.com/watch?v=DsuVLsDyln4

:lol::lol::lol:

Anything "destroyable". Cardboard is a fave but watch out..my other bun used to sit and eat cardboard like it was hay so i stopped giving her it since i was worried it'd clog her up.
Fiver loves those "edible logs" you can buy from P@H. Tbh he has all sorts of toys and logs and whatnot but he gets bored of them after about 3 minutes.