Spelling City : this site allows you to enter your weekly spelling list (and save it) and play different games with the words. My students loved playing these games on the SmartBoard. This was also great because they usually got done with their spelling workbook page quick and we would play games until the bell rang to go home(spelling was out last subject).
United Streaming : I was a huge junkie to this site last year. It had tons of great videos that went along with out grammar lessons. Sadly though I hear our district isn't renewing our membership.
Waltke's Web : I love this site and am very sad I am not teaching ELA this year, but I have been sharing the site with other teachers I know. If you use the Scott Foresman Reading Street series this site has PowerPoints, Spelling City word list, Partner Read Sheets, and Weekly News Letters for every unit for K-5. It was heaven sent!
Brain Pop: This is another site our school used. I rarely used it, but I know several teachers who loved it. I just couldn't ever remember the password for it.
Ed Heads : My class loved the brain and hip surgery games on this site...did I mention I was ELA. Yeah, we used it to play and not for ELA purposes haha.
If y'all have any sites I can use teaching Social Studies and Science leave them in a comment, I am totally lost and have no idea what I am going to do this year.