I have a pop-up telling me that there are "Updates Available" and asking me if I want to install "now or try tonight?". Before Mavericks, I was able to see what the updates were. Is there a way to do it in Mavericks?
Clicking anywhere on the alert (other than the buttons) will open the Mac App Store's "Updates" tab, listing the updates available and their descriptions. If the alert is not open anymore, you can find it in Notification Center under "App Store". When you find it, click on it to see the list of updates.