It's so nice to see grammaticalisation and form-function reanalysis in progress. Errr... I think.

House news - we now have a phone, the main delay caused by the engineer not knowing where a big pipe of wires came out. Broadband apparently appeared first thing this morning, but since I had to come into work to read my email I didn't know about it then. (Actually, given that we've just had a system "upgrade" here, it might have been better to have stayed at home in any case). First major disaster was the downstairs neighbour complaining of water coming through our ceiling. We had a plumber/odd-job-man come out Saturday morning and spend three hours under the bath fixing the makeshift repair that the previous owner must have done about, oh, three or four days before moving out. Nice welcome present for us, oh yes. Anyway, should be fixed now; no all we need is for someone to plumb the gap that subsequently appeared in my bank account.

+w

Knobbly] I must admit i didn't look it up - I just went off the sense of most of the 'en-' words I could think of. I still can't think of an example for making smaller, though.
Another contender for your sense c) is 'tangle' and 'entangle', though according to Webster-Merriam Online 'tangle' is an Anglo-Saxon shortening of an old French verb 'entangler'.

*waves red rag* Can I argue for 'to Google' as one useful example of verbification? I can't think of an alternative that isn't a clunky noun-phrase - to look up on Google, to research on Google, to scope (out) on Google, etc.

I think "to Google" as a verb for "to search on Google" is OK, but only informally. I use it myself. However, it has become synonymous with "to search on the Internet, regardless of search engine used" which plays into the hands of those evil corporate types.

It has, of course, an friend in "to hoover."