For a standalone desktop client, you might be waiting a good while. However, I believe the Chrome browser extension is designed to work off line. It’s identical to the online experience, and is a much more dependable platform than other thin alternatives, like adobe air for example.
In either Springpad or Evernote, look for clippers that allow you to save directly to the application when you are at your desktop. This saves substantial time clipping and saving, and does the online sync in the background. Otherwise, the latest clippers are saving directly to the online service, which might present less conflicts, but can really stall the process of collecting stuff.