Some years ago I composed some tunes for the Pokemon Opal project. Though the project itself is at a standstill for the moment, you can grab my tunes all from one spot. Better yet, you can listen to them for free. The ones I composed for Pokemon Opal are "A Groovy Grove" and "Smiling Sands". To get there, click the Home link above, then click the big bandcamp button.
You can check out the Pokemon Opal project on the PokeCommunity forums: