Glogster can be used to create online posters. The posters can actually include video and sound, also weblinks.
Note the link near the bottom right of the page to the Educator Resource library which includes examples of uses of Glogster in the classroom.
Click download for a pdf.
There are examples of Glogster posters from students around the world on this Wiki.
(Note that the wiki is a Wikispaces wiki).
Traci Blazosky has written a Glogster tutorial which includes instructions on registering with Glogster.
Russell Stannard has made a comprehensive series of Glogster tutorials as part of his training videos collection.
(To print your poster, with the poster displayed, right click and then choose Print.)
A few more great Web 2.0 tools for posters
http://www.band-flyers.com/
http://letterpop.com/
http://www.mybrochuremaker.com/
http://bighugelabs.com/
http://www.squidoo.com/sign-ticket-poster-maker
Some are better than others, but my students usually choose their own as each has different features that suit different types of learners.