NetShare is back in the iTunes App Store after being pulled by Apple for unknown reasons.
If you're interested in tethering your MacBook to your iPhone and you're certain you won't run afoul of your carrier, you might want to check it out here.
UPDATE: Well, that was short lived. NetShare has once again been pulled form the iTunes App Store. Nullriver states on their site, that as of August 1, they still have not received word from Apple on why the app was pulled. Apple has yet to comment on the matter.
Links:
[1] http://www.maclife.com/user/rbaldwin
[2] http://www.maclife.com/article/news/netshare_mia_app_store
[3] http://phobos.apple.com/WebObjects/MZStore.woa/wa/viewSoftware?id=286541579&mt=8
[4] http://www.nullriver.com/