I know this is an old question, but as I found it via Google I think it's worth mentioning something like Context Free Grammars in addition to Markov Chains.
My understanding of Markov Chains is that they create the "next" item probabilistically only according to what the "current" item is. Perhaps I'm mistaken, but I don't see how this would ensure that the result would follow grammatical rules.
For instance, I usually see Markov Chains suggested as a way of creating "English sounding" words. If you create a Markov chain using letters from a dataset of English words, the output would be a word that sounds English, but it wouldn't necessarily be a real word. I believe the same would be true of sentences- you can generate something which may sound ok, but it may not be a grammatically correct sentence.
Context Free Grammars (or possibly also Regular Grammars?) might be a better candidate, since they generate sentences according to a defined ruleset. And it would be easy to populate it with your own words, as the original question requests. The downside is that you need to define these rules yourself, rather than relying on a dataset. It's been a long time since I've used a grammar to generate an English sentence, so I don't remember how hard it was to get good / varied responses.
