View contents of a dll

Telerik just came out with one:

http://www.telerik.com/products/decompiling.aspx

They said that it will ALWAYS be free. They released it in response to .Net Reflector's change to a pay model. Right now it is in an open beta (free to download now) and it works great

Edit: as of June 2014, "free" means you must use their bootstrap installer that attempts to bundle other (nonfree) applications. Also, you must register with their "Support System" to complete the install.

DotPeek is awesome and free.