I use starfall.com a lot in my classroom. They have many reading activities for students of all abilities, and we do their calendar activity as part of our morning meeting on our SMART Board.
I love spellingcity.com! You can put in your own spelling lists and have students play games with them online. They can even take a spelling test online. It works great if you have leveled spelling lists.
I have my spelling lists on both spellingcity.com and kidsspell.com. They are listed on my website and many of the children practice their words this way.