Uwe Ricken has a series on the much-maligned heap:
This article is the beginning of a series of articles about Heaps in Microsoft SQL Server. Heaps are rejected by many database developers using Microsoft SQL Server. The concerns about Heaps are even fuelled by Microsoft itself by generally recommending the use of clustered indexes for every table. Globally renowned SQL Server experts also generally advise that tables in Microsoft SQL Server be provided with a clustered index.
Again, and again, I try to convince developers that a heap can even have advantages. I have discussed many pros and cons with these people and would now like to break a “PRO HEAP” lance. This article deals with the basics. Important system objects that play a major role in Heaps are only superficially presented in this article and described in detail in a follow up article.
I’m generally in the anti-heap camp, but I can acknowledge that there are situations in which heaps are better—I save my dogmatism for other things, like hating pie charts and loving representations of things as event streams.