Make sure that your image compression is set to its lowest setting. When you go into the Menu function to set your Image type (TIFF, HQ, SHQ, etc.), your image compression setting should be 1/2.7 if shooting .jpg or 1/1 if shooting TIFF.
Regardless of your Sharpness selection, if you're shooting at a "standard" image resolution (1/8), your image will come out looking soft due to the camera compressing the image as it writes it to your storage card.
Try shooting in TIFF mode, at max resolution, with the compression setting at 1/1....HUGE difference!!
Also, keep in mind that when resizing your images, the resampling function in ALL software packages will in fact delete information out of the binary image data in order to adjust to a smaller image size. The result? Less sharpness. Adding a touch of sharpness to your image after resizing it should bring it back and really make it pop.