RSS feeds, Google Alerts with "site:joblink.com", Wachete if you need an app for it, limited to 5 for free, OnWebChange up to 3, bookmark all in a folder and open all on tabs.
I don't believe Google Alerts will work for all job sites, but if can also be used for searching for specific jobs not just career portal updates.
If you want to stay on top of updates to a certain page, there are tools to notify you:
Just to name a few. Save your F5 key brother!