Legend has it that Gregor Mendel's classic paper on the genetics of the pea plant languished in the obscurity of a Czech journal for 30 years—if email alerting had existed in his day, dissemination of his results might have proved a little more rapid.
The 800 lb gorilla of such services in the United Kingdom is Zetoc, which uses British Library data indexing the contents of more than 20 000 journals and 16 000 conference proceedings each year to provide email searches on keywords.
You need an Athens password (www.athens.ac.uk/), which is a free privilege for NHSnet users in England, thanks to a deal with the National Electronic Library for Health (www.nelh.nhs.uk/).
Once you're in, you can set up unlimited numbers of email alerts. However, the slightly tedious restriction that any one search can be on up to only 50 journals means that many specialists will have to set up multiple searches to cover the range of journals that could potentially carry articles of interest. After all, the whole point is that you are not limited to the journals to which your library subscribes.
If Athens is not available to you, there are a number of services based on the National Library of Medicine's PubMed service. The best of these is probably BioMail (www.biomail.org), though there is little to choose between it and its competitors JADE (journal abstracts delivered electronically, www.biodigital.org/jade/topic.htm) and PubCrawler (www.pubcrawler.ie/). PubCrawler, however, has the best slogan: “It goes to the library. You go to the pub.”
Setting up keyword searches on all services is easy, although the obvious problem is that, while it is all very well for specialist arcana, there's no easy way to achieve breadth if your interests are not easily encapsulated in a few key terms.
Zetoc only sends you the indexing info (title, author, journal, volume, issue, page number); most journals on PubMed will also give you an abstract. This still means, in most cases, an expensive paperchase to a document ordering service if you actually want to read the article. Roll on the Public Library of Science initiative (www.publiclibraryofscience.org/).