When you go to a festival you want a rucksack that's big enough to hold all your essentials but you don't want it to be too big because you can then use it when you're away from your tent. It also needs to keep the water out because there's nothing worse than wet clothes or a ruined iPod!
Rucksack which have an additional daypack are ideal. You can keep all your clothes and other essentials in the main compartment and you can zip-off the daypack for the items you want to keep close to you like your purse/wallet and mobile phone etc.
We have lots of suitable festival rucksacks, but here's a few we think are perfect:

for guys
The
Berghaus Freeflow 30 Plus 6 Rucksack provides you with a main compartment which fits 30 litres of belongings as well as the extra 6 litre daypack which you can take to the music tent with you.
for girls
Because women tend to have more stuff to take with them, we suggest this cool Womens
Freeflow Pro 40 Rucksack in Amethyst from Berghaus.
You've got 40 litres for all your essentials and let's face it, it's a nice girly colour too.
excellent value
The
Kohima Wheelie Bags from Lifeventure come in men's and women's versions. These are perfect if you need more space for all your camping gear. Plus you can wheel them along too, so they're great if you've got a bit of walking to do before you can pitch your tent.