I'd have to agree with Blaat. This year was an overall weak year for soundtracks without too many standouts out there to praise. But even then, I can pick out 5 that have been really enjoyable:
Romeo x Juliet: Technically, this one counts because it wasn't released until 2008. Sakimoto combines his mastery of medieval themes together with anime music and the results are just damned
gorgeous.
Spice and Wolf - Somehow, the themes here just work together really well and as I listened to it, it keeps me entertained because it's so subtle, yet so wonderful.
Macross Frontier - Yoko Kanno delivers with yet another beautiful orchestral album that mimics many of the best themes from Western film music. Hell, you can hear her quoting Hans Zimmer in one of her pieces and some of the others take a hint from John Williams.
ARIA the Origination - A very pleasant soundtrack that absolutely surprised me because I thought they'd run out of themes to use for that anime series. The piano and guitar work from the Choro Club and Takeshi Senoo make for a really peaceful and mellow album that matches up with the series completely.
Natsume Yuujinchou - One of those albums that really put you into the mood of the series. While some people might not enjoy it as a standalone listen because of the importance of context, I think this album does a decent job without it because there are many tracks that are able to convey the wonderful feeling of a lazy summer day really effectively. It might not be up your alley, but it's certainly not a boring listen.
At this point, I'd have to rank Romeo x Juliet as my absolute favorite. The Sakimoto fanboy within me cannot resist.