I've read about a move that involves upshifting a couple of cogs in back (to smaller cogs) as one stands and thrusts to help maintain speed when standing.

What dropped me once was a guy in front of me, near the very top of the incline, standing and slowing down as he did so. Literally looked like, in the short time before he was in my wheel, as if he was in reverse. Did some searching on climbing technique and ran across the above.

Quite honestly, in recent riding (~25,000 miles on the Veloce), I've never stood other than to see if I could - felt off balance and never tried it again. One of the advantages of being overweight and then loosing the excess (235->165 in 13mos) is that one is likely to be left with a fairly strong set of leg muscles from lugging all that lard around for too many years.

I dropped the weight riding a Trek 7500FX. I eventually replaced the stock cassette (11-32) with a 12-27 but before I did, I got in the habit of trying to spin when climbing by using the triple crank's 26 tooth inner chainring and a large cog in back. I didn't climb fast but as strength improved and weight dropped, was able to increase speed up most hills while still maintaining a fairly quick cadence.