Since the iPhone's release the only real choice for browsing with has been Safari. If Opera get their way though this may soon change as they prepare an iPhone version of Opera Mini. An official announcement should be made this weekend at the Mobile World Congress.
Opera's plan is to include their tabbed browsing amongst other features such as their password manager and the "Speed Dial" for quickly accessing favourite and frequently visited websites. The Speed Dial feature is one which has also been copied by Google for their Chrome browser and is certainly a nice feature to have.
If Apple accept this browser into the App Store it opens the way for other browser developers to do the same which means we could see Fennec, the mobile version of Firefox following suit before long. At the minute I think it's unlikely that Microsoft would produce a mobile version of their browser to run on the iPhone due to them not having a current Mac version of their browser. It may also change the course of the current round of browsers wars so that their resources may become further divided between their desktop and mobile versions (with the exception of IE which is bound to stay behind the pack for some time yet). I think it will be interesting to see how mobile browsers change now and how they will converge towards their desktop counter-parts.
