One sight that I like to use in my classroom is
http://sigsx4.wikispaces.com/Social+Studies. It is full of ideas for social studies and science lessons, websites, games, videos and more just for 2nd grade. They have organized it very well. All of their lessons and ideas are connected to the state GLCE's. Social studies and science materials are hard to find for the lower elementary students, so I have enjoyed this one.
A second sight I found when I was looking around was Mrs. Goneau's 2nd Grade Wiki.
http://mrsgoneau.pbworks.com/ They are a second grade class from Random Lake, Wisconsin. I found her sight fun to look at and great for ideas to incorporate with my classroom. She organized her Wiki by classroom projects, sites and resources. I liked how she had her classroom projects from the last three years in the same Wiki. I know when I had a classroom wiki, the students from the last year asked if they could still get on the sight. They were disappointed to hear that I didn't keep the same one this year. She had several sights that she linked to her Wiki I thought would be fun to check out. She used Slide.com to make a couple different slide shows of her class. She also used a site called Podbean.com.
A third site I found was
http://hcselabs.wiki.hoover.k12.al.us/2nd+Grade+Links. This Wiki was very organized. It had math, language arts, science, socials studies, art/music and health. There were several links in each of these areas. The wiki was also organized by grade level. This sight looks like it was made by someone in Alabama.
I used a wiki in my classroom last year. The kids/parents loved it. This year I switched to a classroom web page instead. I thought it was easier to use and make it look the way I wanted to. I couldn't get my Wiki to look "cute" the way I wanted to. As I browsed through a lot of these other wikis, I noticed many of them were able to make the look cute.