We want icons for several aspects of our product, including:
iPhone style icons (ie Squareish, semi-glossy) might work well here, but the final decision is up to the designer obviously.
Icon designs we like: Adobe CS4 icons, iPhone stock icons, MS Office 2007 icons
The key is that we want all these icons to be consistent in theme. Colors are flexible (use any colors you want) as well as graphic metaphors.
Keep in mind that these icons should be vector based and SCALABLE so that they can be featured in large version alongside the app in an "app store" interface, but also look good in small versions.
Many of these icons will be featured on our website, and the winning designer may be contacted to create new icons as we expand our product offering down the road.