It's really so easy, especially since we're only dealing with small amounts of data here (a typical wallet is only a few MB).
Encrypt your wallet (either with your Bitcoin client if it supports encryption, or with free solutions like 7-Zip or TrueCrypt) and email it to several accounts on different email providers (e.g. gmail, yahoo, and hotmail) and/or put it in a Dropbox folder. As long as you remember your encryption password, this way your wallet will be absolutely 100% safe.
And keeping your wallet SAFE consists of two different, yet equally important aspects:
- not losing your data (thus losing your bitcoins)
- making sure nobody else can access your data (so they can steal your bitcoins)