Apparently you can also use vinegar, salt, sugar, and corn meal, all of which have different effects on plants. Boiling water sounds OK, especially for spot control, but I'm thinking more of something residual, so it'll keep stuff away for a while.
The various commercial products, which have a long lasting effect, appear to be mixtures of glyphosate (aka Roundup) and either flufenacet/metosulam or oxadiazon/diflufenican. As far as I can work out, they're intended to hit different growth periods. Since glyphosate is absorbed through leaves, it's most effective towards the end of summer, when the plant is most extensive, whereas some of the others are pre-emergence herbicides, and stop the seeds from growing at all. So they're probably a mixture of contact and systemic herbicides, but finding out the exact nature of the products is an exercise in extensive Googling!