95 blazer revs itself

my 95 blazer has been idling hard, and backfires occationally. Now it started reving itself, and won't start.

--any ideas??!!

with other vehicles I've worked on, vaccuum hoses being loose, or a vacuum leak of any kind, can be a common cause of the revving and dropping off. That and something related to you mass air-flow sensor. Make sure the connector isnt dirty, and is fully plugged in. Those are the quickest things to check before you get dirty. If it is in fact plugged in fine, could possibly be a bad sensor.
No check engine light yet though? Seems odd.

fyi-check for a vacuum leak by spraying vacuum hoses, and connections with a small spray of starting fluid. If the engine revs when you do so, you have a leak wherever you're spraying

ps- for the backfire and rough idle, when's the last time you did a tune up? wires/plugs/cap/rotor/filters

does it sound like you're not getting a spark when you attempt to start it?