If you have a less-then-stellar credit history, your water company or another utility might charge you a security deposit before opening a new account. These deposits can run into hundreds of dollars. Laws differ from U.S. state to state, but generally the utility must pay back the deposit, with interest, after 12 months of on-time payments [source: Cat Le]. If you qualify, but haven't received your deposit refund, get on the phone and you could be the recipient of some quick cash.
If you move a lot and have opened several bank accounts and utility accounts in different states, you should also conduct a search on MissingMoney.com. The site can run your name through national databases of unclaimed assets and property.