When I open raw/NEF images in Lightroom, they appear washed out as compared to viewing them in Picasa (same computer monitor). If I open JPEGs, they're fine in Lightroom.
Anyone know how to fix this?
This is expected, because the raw image has had no corrections/edits made, which means you are able to do all the edits the way you want. With RAW you gain control of the process at the expense of more post-processing time.
Picasa will apply corrections on the fly, so you are seeing the auto-corrected version of the raw file in picasa, but the direct raw file in lightroom (as mentioned by Alan lightroom does apply very minor corrections, but it is essentially just the image straight off the sensor).
The jpeg has had standard curves/color balance correction/sharpening applied in camera prior to the conversion to jpeg.
You can use "presets" in lightroom to set the basic adjustments that you want to do. These are sets of edits/corrections that are saved and can be applied as a group to any image. You can create your own, or search around and find presets that will create different looks.
When importing pictures from my D7000 into Lightroom 3, I've found that I can get the same look in Lightroom as with out-of-camera JPEGs if I change the "profile" setting in the "camera calibration" section at the bottom of the develop settings. E.g. if I took the shot with the picture control setting on the D7000 set to vivid, I need to change the profile in Lightroom to "camera vivid". One way to do this is to apply a develop preset during import.
RAW files are not images yet. They are usually missing color-components on each pixels, so to see a RAW file it must be converted into an image.
Different software apply different conversions to show you the RAW files as if they were images. That is why your RAW files appear different in Picasa and Lightroom. The software is pretty much free to do what it wants at that point.
Some RAW files actually have a JPEG embedded (for preview purposes). In this case it is easy for the software to show you something. This depends on your camera. Sometimes it is a small preview (thumbnail), other times it is a full-size image. When you have only the small preview, you will sometimes see your images change in some software which loads the small JPEG as a preview and then uses the RAW data to render.
If you ONLY shoot RAW and thought not to care about image parameters (WB, Color, Saturation, Tone, Hue, Contrast, etc... depending on your camera), then you should know that if your files have an embedded JPEG, they use those parameters anyways. These parameters are also often used as a default RAW conversion when displaying RAW files and importing them. Depending on those settings, then the preview for your RAW files can look drastically different that what you had in mind.