In this context, I believe "dérive" is a reference to the practice of "wandering", originally coined by the Situationists as an art practice, and often retained as a French word in English. It means to drift, obviously, in particular where this drifting is directed by random signs rather than planned in advance, so here it means "a set of random thoughts"

Even though this is not a physical "derive", I believe it is attempting to convey the same meaning.

Refs:
Theory of the Derive (Debord)
On the early situationist practice of urban drifting. ... One of the basic situationist practices is the dérive,(1) a technique of rapid passage through ...
www.bopsecrets.org/SI/2.derive.htm

Situationist International
Derive was a favorite practice of the Dadaists and the Surrealists. The derive, or drift, was defined by the Situationists as the "technique or locomotion ...
www.uweb.ucsb.edu/~setzer/page1.htm

http://www.uweb.ucsb.edu/~setzer/page1.html

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Note added at 40 mins (2007-10-17 00:22:05 GMT)
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Wikipedia entry (http://en.wikipedia.org/wiki/Dérive) notes this is sometimes translated as "drift", which could work, but for a contemporary art theory article, I think leaving "derive" as is will be understood and is more appropriate.

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Note added at 16 hrs (2007-10-17 15:54:50 GMT)
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It sounds like the right theoretical environment for keeping "dérive" - even though the word has become a term in English because of the situationists, I don't think this necessarily narrows the meaning too much, ie excludes it from being understood in the more ordinary sense it has in French. The problem is more, as Vaughn suggests, that English semi-equivalents *do* seem to narrow or skew the sense. I'd compare it to a word like "jouissance": there are English words for this and sometimes they should be used, but in certain contexts its appropriate to retain all the resonance of the French. But I do go on...

If I had to pick an English word, I'd go with "drift", because, like drifting ships, this means from that from a given point one goes off course, buffeted by currents beyond one's control.