Yep. No need to download or jailbreak, just go to the URL. If you’re looking for great webapps to check out, try Launchrz you can also collect your favorites there on a “launchrz page” for fast and easy access in the future, which is maybe what you are looking for.
Web Apps are currently not downloadable but may be added to the homescreen as Spargett mentioned.
If you don’t like having to go online for other applications just wait. Come May or June (I can’t remember which right now) with a new software update Apple will be adding the ability to download third party applications to the iPhone and iPod Touch via an online store similar to iTunes.
AppSafari seems to be pretty complete listing of webapps and displays in a webapp version when viewed from the iPhone.
In the App Store is an app called ”Web Apps” which has an extensive database and allows you to bookmark them into a directory, thus saving space on your home screens.