Arunn has a post on Quantifying Research Quality through Article Level Metrics.
The beginning of the end for impact factors and journals, a neat online article by Richard Smith , explains the newly introduced ALM indices with examples. Another recent article published in PLoS by Cameron Neylon and Shirley Wu  discusses the pros and cons of the newly introduced ALM indices. But both these articles leave out in their discussion, certain key journal requirements for proper functioning of the proposed ALM and their related shortcomings.
Also, journal impact factor is being seen as a very poor measure of article impact. One distinction is essential in such generalization. Because we are able to debunk the efficacy of impact factors, we are not debasing the reputation earned by research journals.
In this article, we discuss the efficacies of the proposed ALM indices, journal impact factor contrasted with the prevailing journal reputation and related issues in detail. In the summary, we provide possible rectification measures for ALM.
- Sachin Shanbag has one on Quantitative v/s Qualitative Evaluations: Impact Factors and Wine Experts:
I think they are a lazy substitute for actually reading a person's research and evaluating its worth individually. While it is fashionable, and getting increasingly so, I've never really been a big fan of using purely quantitative factors to measure the worth of an individual, university, or country.
You wouldn't necessarily think that the musician who sells the most records, or has the most covers made is necessarily the best (that would rate the likes of Back Street Boys over bands like Dream Theater).