Check out the beta and tell us what you think: ethereumwallet.com/beta/index.html
I'm the CTO of KryptoKit, the software company that makes RushWallet and the KryptoKit chrome extension. We're big fans of Ethereum and we've thrown together an instant ether wallet (similar to RushWallet) that allows you to easily send and receive ether from your browser or smartphone. This is very early software, so it is definitely "use at your own risk." We recommend using the wallet with small amounts only--this is still Frontier after all!
Here are the details of how the wallet works:
When you first use the wallet, you generate a random private key by moving your mouse around the page. At this time we do not support importing or exporting json wallets--you must create a wallet on the website in order to send or receive funds via the website.
Optionally, you may add a password during wallet creation
The page will create a unique and secret URL that you must bookmark in order to be able to access your wallet later. If you lose your URL or forget your password, there is no way to recover your funds.
The secret part of the bookmark (after the '#') is never sent to our server and exists only locally on your machine. The password is not stored anywhere--when you type it in it is combined with the secret part of the URL to create a private key. We do not send this private key to the server at any time.
Development work is ongoing, and we hope to add QR code scanning for Android devices soon.
Once again, be aware that this is VERY beta software. We try to be careful, but we cannot be responsible for any losses due to software bugs, cryptographic weaknesses, or other errors. Bookmark formats may also change going forward. Use this software at your own risk.