Publisher alerts are usually faster than database alerts!! Publisher websites are the first place information is made available. This information is then sent to database vendors; however, some databases are only updated monthly or quarterly. Also, publishers often provide information on research articles while they are still "in press" but databases do not usually include content until after it is officially published. The drawback to publisher alerts is that they usually cover a fairly small number of journals while database alerts can cover several thousand journals.
NOTE: Publishers offer the ability to sign up for alerts about articles in all their journals/publications. They do not require you to have a subscription to the journal to receive alerts.
The following publishers offer alerts via email and RSS feeds. Some also offer the ability to become fans in Facebook or follow via Twitter. Whenever possible, the link below leads to a page of information on how to set up alerts.