Many publishers of scientific journals offer alerts on the Table of Contents of their journals. You can find a list of the most important publishers and aggregators on the library website: E-journals A-Z, choose Publishers' sites (http://library.wur.nl/desktop/vrr/publishers.html) . Publishers in this list like Blackwell, Springer, Wiley, etc. offer ToC alerts (sometimes also called e-alerts) via their respective websites. Setting up alerts via a publisher requires registration on the website of that publisher.
If you want to set up ToC alerts for many journals, the option via My library is easier than via a publisher, because My library requires one single registration only. However, a ToC alert via a Publisher comes mostly quicker that a ToC alert via My Library. Bear this in mind if you need the information as soon as possible.
An explanation on how to set up ToC alerts can be found in the help files on the publishers' websites. For example, for setting up ToC alerts on ScienceDirect, which is the home of all Elsevier Science journals, the following instruction is given: http://help.sciencedirect.com/robo/projects/sdhelp/vol_iss_alert_list.htm