Allison Robert, druid columnist extraordinaire, has written up a three page guide on the basics of healing as a tree over at wow.com.
Very good, and good to see this sort of resource out there, especially with everyone trying to run as a healer or a tank under the new LFG system. (The other big guide on tree healing you should read is Lissanna's, over here at restokin.com.)
As Allison alludes, some of the druid resto kit is quite situational. Improved Tranquility, for example, is well worth taking if you only run 5-mans. Tranquility has saved me a few times in Heroic Halls of Reflection already. It's fairly useless for raids, though, particularly since it will only work on people in the same party as you.
My only other contention is that you should think twice about getting the Glyph of Wild Growth. This increases the maximum number of targets for your Wild Growth from 5 to 6. All of them must still be within 15 yards of your primary target, however. My problem is that, as a 10-man healer, I rarely see 5 people, let alone more than that, clumped up enough to take full advantage of Wild Growth. I still use it. A lot. I just don't think the glyph would improve it for me.
Allison actually responds to this concern in the comments of her column (three cheers for responsive writers! hip hip hurray!). She agrees that a lot of recent fights, especially in ICC, encourage groups to scatter, especially the ranged. However, as she points out, if you have more than 5 melee, or if you're doing fights with large amounts of raid damage where the raid still stays fairly close together, the extra Wild Growth landing can be a godsend. I may try switching out Rapid Rejuv for Wild Growth tonight and see how it goes.
EDIT: Lissanna just posted in response to my comment as well. She carries a stack of Rapid Rejuv and a stack of Wild Growth glyphs with her, and switches out fight-by-fight. Her other two glyphs are in line with mine: Nourish and Swiftmend. I may start carrying a few of the first two with me to experiment a bit.