http://antwrp.gsfc.nasa.gov/apod/ap970430.html
Map of milky way galaxy in radio waves emitted by carbon monoxide.

http://antwrp.gsfc.nasa.gov/apod/ap011020.html
Map of milky way galaxy in radio waves, 408 MHz.

http://antwrp.gsfc.nasa.gov/apod/ap000517.html
Map of sky showing milky way in far infrared.

http://antwrp.gsfc.nasa.gov/apod/ap000518.html
Map of sky showing milky way in near infrared – note difference from far infrared image.

http://antwrp.gsfc.nasa.gov/apod/ap010202.html
All-sky view of milky way in optical light.

http://antwrp.gsfc.nasa.gov/apod/ap960709.html
Image of a spiral galaxy in ultraviolet light, showing regions of recent star formation (hot, luminous high mass stars)

http://antwrp.gsfc.nasa.gov/apod/ap960102.html
All-sky image showing X-ray sources in plane of milky way galaxy – an older image.

http://antwrp.gsfc.nasa.gov/apod/ap000819.html
Another older image of the X-ray sky, from a different satellite/telescope than in the previous image.

http://antwrp.gsfc.nasa.gov/apod/ap970501.html
All-sky view from low energy (0.511 MeV) gamma radiation showing distribution of annihilation radiation from electron/positron pairs. The detection of radiation at this energy implies the existence of lots of positrons, the anti-particle for the electron. The mystery in this picture is the blob of emission (positrons) above galactic center.

http://antwrp.gsfc.nasa.gov/apod/ap960529.html
All-sky view from modest energy (1 MeV) gamma radiation showing discrete sources in and outside the galaxy.

http://antwrp.gsfc.nasa.gov/apod/ap960724.html
All-sky view in 1.8 MeV gamma radiation shows the distribution in space of radioactive aluminum-26, which gets manufactured in supernova explosions (both type Ia and type II). The half-life is about 720,000 years, so the image represents supernova results spanning the last several million years – recent history in astronomical terms.

http://antwrp.gsfc.nasa.gov/apod/ap010811.html
An all-sky view from high energy (>30 MeV) gamma radiation showing discrete sources in and outside our galaxy.

http://antwrp.gsfc.nasa.gov/apod/ap950623.html
An all-sky view from higher energy (> 100 MeV) gamma radiation showing diffuse distribution in the plane of the galaxy, as well as some external sources.

http://adc.gsfc.nasa.gov/mw/mmw_allsky.html
If you're too impatient to wade through the previous APOD images and descriptions, this is a website that has most of the images on one page, with short interpretative summaries.

http://antwrp.gsfc.nasa.gov/apod/ap011024.html
Argument FOR dark matter in galaxy clusters, based on HST and X-ray images of galaxy clusters. The HST images are in visible/infrared, and the X-ray images show the location of high temperature ionized gas (millions of Kelvin). To confine this hot gas in a galaxy cluster would take an order of magnitude more mass than we can detect from the HST images.