Rendering video with pixel aspect ratio 0.9091 (in premiere CS5.5) I have a video (from my Android Nexus One).  Dimensions are 720 x 480.
The pixel aspect ratio is, according to data embedded in the file, 0.9091.

Now, editing the video and exporting it to a media that says it has square pixel obviously makes the video look 'narrow' on the X axis.

The only way I could edit this in Premiere and export it to MPEG (2 or 4), was to scale each source video up to 109.9% on the X axis (since 0.9091 * 1.09 is ca 1.0).  Premiere doesn't allow me to say that the generated file as a pixel aspect ratio of 0.9091.

This works, but feels wrong.  Especially if I have lots of source videos, to set the scaling factor on each of them.

Is there a better way to do this ?
If you're exporting directly from Premiere, then select the MPEG2-DVD NTSC preset in File -> Export -> Media, as shown in this image. 

Also, it looks like MP4Box will allow you to change the pixel aspect ratio flag in a .mp4 without re-encode.

FYI: 720x480 with PAR 0.9091 @ 29.97fps is the NTSC DV standard resulting in a 4:3 display aspect ratio. Similarly, 720x576 with PAR 1.0667* @ 25fps is the PAL DV standard.

*The actual PAR is supposed to be 59/54, but many apps use 16/15. See here if you're interested.