I recommend using sIFR (or Scalable Inman Flash Replacement) for the headlines with the Futura. For body text, i guess Trebuchet is the closest option.
But check for yourself here.

Seb

Arial Narrow is pretty widely deployed.

Tahoma might be another option.

You could always contact Adobe or Bitstream about licensing their version for use with web embedding. Or, if the client has the money, you could even commission a custom version made to use on the web—it won’t be that crazy expensive to do one font in one weight of an existing typeface.

James, the problem is that most users will not be using a browser that supports web embedding. So far, afaik, it is only safari that supports it, with firefox coming soon.
You could try specifying century gothic, as it is a quite common win font (85% of windows users, according to this survey)

James, the problem is that most users will not be using a browser that supports web embedding.

The last time I checked a very healthy majority of web users are still using Internet Explorer 6.0 or later which supports Embedded OpenType. So most users would be, in fact, using a browser that supports web embedding.

ANY 'light condensed' would likely be a bad choice for body copy text on a web page (or on-screen, in general).

I think light use of the typeface via sIFR for headlines is likely the best bet for now.