Lifehacker have a round-up of recent money saving tips. While much of is very US-centric, there’s likely to be something you can apply to your own situation/locale. One which I know from experience will work here in the UK is the tip to lower your credit card interest rate

While talking with this agent, be firm — tell the agent you’re planning to leave, but would consider staying if s/he offers you a drop in the interest rate to under the other card’s rate. Don’t tell them what card it is – they’re armed with reasons why that’s a bad card for you, and that’s not the conversation you want to have with them. Stay focused on the issue of lowering your current rate.