--In theory, this is not against the Spotify EULA as it still uses your %APPDATA%. --
So I was looking online and I couldn't find anything for this, so I decided I'd make a Spotify Portable application.
I read up on the EULA and apparently Portable Applications are against it, however this 'application' still uses the %appdata% command, so its still technically using computer resources.
Download Link (VERSION 1): [Link removed; it's still redistribution - mod Chris]
Encase you care, the warranty of SPOTIFY does not warrant third part applications, which I'm going to assume this is so anything that may happen is not my fault. Either way, have fun with it.
14. Warranty
We endeavor to provide the best service we can, but you understand and agree that THE SPOTIFY SERVICE IS PROVIDED “AS IS”, WITHOUT EXPRESS OR IMPLIED WARRANTY OR CONDITION OF ANY KIND. YOU USE THE SPOTIFY SERVICE AT YOUR OWN RISK. SPOTIFY DISCLAIMS ANY WARRANTIES OR CONDITIONS OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT. In addition, Spotify does not warrant, endorse, guarantee or assume responsibility for any Third Party Applications, Third Party Application content, User Content, or any other product or service advertised or offered by a third party on or through the Spotify Service or any hyperlinked website, or featured in any banner or other advertising. You understand and agree that Spotify is not responsible or liable for any transaction between you and third-party providers of Third Party Applications or products or services advertised on or through the Spotify Service. As with any purchase of a product or service through any medium or in any environment, you should use your judgment and exercise caution where appropriate. No advice or information whether oral or in writing obtained by you from Spotify shall create any warranty on behalf of Spotify in this regard. Some aspects of this section may not apply in some jurisdictions.