These are all remarkable, but the one that really gets my imagination going is #7 - Straightlist. If they can implement embeddable widgets that can be put into blogs and forums I can see the site picking up a lot of steam, and once they start keeping track of hits on each page the site has the potential to become a reddit for guides
#1 LowDown - http://mcp.r09.railsrumble.com
#2 Hi, I'm - http://hi.im
#3 Omnominator - http://omnominator.com
#4 Thingivore - http://thingivore.com
#5 Neighborhood Watch - http://neighborhoodwat.ch
#6 Techmeets - http://techmeets.com
#7 Straightlist - http://husohuso.r09.railsrumble.com
#8 SmackSale - http://smacksale.com
#9 Nybbl - http://nybblme.r09.railsrumble.com
#10 Last Percent - http://lastpercent.com
#11 Table Surfing - http://tablesurfing.com
Some awesomely ridiculous apps that deserve mention:
http://www.lazeroids.com (online massively multiplayer asteroids). Seriously.
http://www.stomachly.com (restaurant ratings based on bowels)
http://www.celebritypassage.com (tribute site to dead celebs)