|STS-41C Mission Insignia for the Space Shuttle Challenger|
I found quite a few space themed postcards in the Planetarium gift shop at the College of Southern Nevada. Programs are presented on the domed screen very Friday at 6:00 pm, 7:00 pm and 8:00 pm and every Saturday at 3:30 pm, 6:00 pm, 7:00 pm & 8:00 pm. Check their Event Calendar for the current line up. Weather permitting, the telescopes at the Student Observatory will be open for viewing After the 8pm presentation.
Clare has a blog post on the 10 Stamps for the Space Day. Hope I can collect them all some day.
Where the postcard was bought: Planetarium and Observatory at the College of Southern Nevada