My director wants a secondary motion that ramps in speed, ie smoothly speeding up and then slowing down...Is this possible with Premiere?

Easily. Just keyframe the speed in the Effects Control panel. That said, After Effects and some third party apps will do a better job, as PPro will just do a frame blend. AE has an effect called Timewarp that takes a little tweaking and practice, but uses vector mapping to give better results.

I wish it were posible in Premiere Pro, but I don't think it is. Perhaps Peter is thinking about another program. The only work around that I am aware of is to cut the clip into pieces and then add increasingly faster or slower speed to each successive clip. It is not completely smooth, but if you don't jump too far between each clip, for example 100%, 90%, 80%, 70% in four steps instead of 100%, 70% in just two jumps it looks pretty good.

I was hoping for true time mapping or velocity envelopes in the last version of PPro, but it didn't happen. Maybe next version.

Dang it, I screwed up! Lloyd is correct that speed is not key-frameable in PPro. Sorry about that...can I blame it on all the Sudafed I'm taking for this miserable cold?

Lloyd's manual method will definitely work, and you can razor-tool it up as finely as you need to. It sounds tedious but for one or two brief scenes it really would take only a few minutes since the speed adjustment for each little piece just takes a couple of mouse clicks and entering the speed percentage.

I thought there might be a work-around using the Posterize Time effect, but alas, the only keyframe allowed for that effect is "Hold"...which is effectively "None." If you have too much footage to do this manually, AE (among others) will give you much more robust control. Again, sorry for the mis-info.

Plus Adobe Premiere speed handling is really, really lame :( in terms of interpolation.