One thing I've noticed is that when a new Apple product comes out, accessories tend to be a bit scarce for the first couple of months. That may not be the case when the

iPhone 3G rolls out next month.

Belkin and Speck have already announced several iPhone 3G cases, and soon others will follow. Since the aluminum back on the iPhone 3G will be replaced with a plastic one, it may be a good idea to start looking at your options now. Here's a quick preview of what you can expect next month:

Speck ToughSkin: This rubber case has a textured surface that gives you a better grip on the iPhone, and protects it from accidental drops. The bottom of the case flips back for easy docking, and a removable belt clip is attached to the back so you can carry it however you want. This thick, rubber skin will be available in July for $35.

Speck SeeThru: The hard shell cases are so thin, they don't add bulk to the phone. Inside they have built-in rubberized side strips to keep the phone in place, and the bottom of the case slides off for easy docking. They'll be available in several colors in July for $30.

Belkin Sports Armband: You're going to want to take your iPhone 3G on runs, so this sports armband is great because it's lightweight, hand-washable, and water-resistant. It also gives you full access to the iPhone screen and has a key pouch on the side for convenience. It will sell for $30 upon release in July.

Belkin Micro Grip: My problem with some cases is they're not easy to grasp, that's why I like anything with a textured surface like the Micro Grip case. The case itself has cut-outs for the iPhone's controls and ports, and stays on while you charge your iPhone. The pattern on this case is very busy in black and white, but the pink version isn't too bad. Both pink and black cases will be available for $25.

Belkin Eco-Conscious Formed Case: Everyone's trying to be eco-conscious these days, so Belkin created a leather case constructed with natural-felt interior. The case gives users access to the iPhone's screen, and all its controls as well as the dock connector for easy charging. Again, you don't have to remove the phone from its case to charge it, which is always nice touch. Price will be $35.

You can see the complete list of all the iPhone 3G Belkin cases here. All of them will launch in the U.S., Europe, Asia, and Australia.