There is no need to wait to get updates via your desktop iTunes. You can check for updates anytime directly on the iPhone. Choose the icon ‘App Store’, then choose the ‘Updates’ along the bottom right.
The system will then automatically check all of the apps you have installed (this option wont download the updates for application that you bought and then removed) and present you with a list of apps to download/install.
Choosing one will give you a outline of what is included in the update. This is written by the developer so it will most likely heavily push the new features and downplay any bug fixes. Tap the ‘Free’ button, which then change to a button that reads ‘install’ which you will have to tap also. You can only download one application update at a time, unlike iTunes that allows bulk downloads.
The system will take you back to the Launcher window that had the previous installed application. You will be asked for your iTunes account password – upon entering that, the icon for the updating application will have a blue progress bar showing ‘downloading’ and then ‘installing’.
If you don’t choose to install all of the apps available to update, a small number will appear over the App Store icon as a reminder what you have left.
You can download just the ones you are interested in. Then, let iTunes download and install the rest on your next sync. Either downloading updates with via the iPhone / Touch or iTunes will cause that number indicator to go away.