It's common for some apps to be updated quite frequently by the dev's. While the market is open, select Menu/Settings and turn off Notifications.
The market will still show updates are available when you select My Apps.
If the aps are updating by themselves, open the app and select Menu/Settings, and see if there is an auto-update option you can turn to Off.
Rom Manager is notorious for auto-updating uncommanded
so I suppose some other apps are as well.
One more note, avoid selecting Update All if you have more than 3 or 4 apps that need updating. Updating numerous apps can sometimes lead to continous updating issues.