Doesn't exist anymore, but there is a way to get 3.2.6 - through developer.apple.com/downloads - after free registration filter for 'developer tools' and type xcode - you should find the xcode_3.2.6_and_ios_sdk_4.3.dmg others have mentioned. It's 4+ GB though...
Next, open a terminal, run xcode-select --install, and click the Install button to install the required command line developer tools. Don't worry if you see a message telling you the software cannot be installed because it is not currently available from the Software Update Server. This usually means you already have the latest version installed. You can also get the command line tools from the Apple developer website.