One Itunes account for me and my wife

Help for what?

Just sign in to the account from which you wish to purchase:

http://manuals.info.apple.com/enUS/iPhone_iOS4_UserGuide.pdf

You can sync as many ipods/iphones as you like to one computer/library.

That is very vague.

What do you mean?

What have you tried?

Does itunes recognize that the iphone is plugged in?

What happens?

Error message?

What does it say?

You can "share" iTunes content within the same household. That might be a better approach with two separate computers & iTunes accounts. The stuff on your wife's computer is grayed out, because by design you can sync iTunes content with the iPhone on ONE computer at a time. So, if you want to "share", do this:

1. First disable auto-sync under Preferences>Devices in iTunes(under the edit menu if using Windows) on your computer.
2. You sign out of iTunes & sign your wife in.
3. Connect her phone...DO NOT SYNC!
4. Store>Authorize this Computer.
5. File>Transfer Purchases.
6. Eject her phone.
7. Sign her out, you sign back in.

You can now sync and add whatever content you want to each device. Just remember, all app updates to any apps obtained with her account MUST be done by signing into iTunes using her account, update the apps in question, sign her out, you sign back in.

That's all you have to do.