The ODOT Freeway Speed Map is now available (or, you can just use a shorter link, http://tinyurl.com/dud3q. A full-scale version's also available.
I had been hoping for something like this, and have a version for my PalmPhone which works for the Seattle area. Fortunately, the ODOT version does, too, although the Washington equivalent is clearer on my PalmPhone, with wider color stripes. You can also see when comparing desktop versions the version for Pugetopolis offers more detailed speed information.
Also, here's another traffic link, for the PDXinfoNet Traffic Report web page, a plaintext page easily read by cellphone browsers.