1) Are you paying unnecessary tax on your bank or building society interest?
For the last week or so HMRC have been running a campaign to remind people who are not taxpayers - including many pensioners - that they should register with their bank/building society to get their interest paid without tax deduction. Banks & building societies take 20% tax off before paying their interest to their savers. So someone who is a non-taxpayer then has to claim it back from HMRC or they can register with the bank/building society (with a form R85) and get it paid without tax deduction. You can also get free tax advice from Tax Help for Older People if your household income is less than £15,000 per year and you are a pensioner.
2) Make sure you are not paying national insurance once you have reached state pension age. This is particularly important if you have been or are still self employed.