Utilties

• Resharper needs no introduction
• Expresso excellent regular expression designer/tester
• Notepad 2 also see here for instructions on replacing Notepad with Notepad 2
• Notepad ++ another editor
• PSPad editor for developers
• Programmers Notepad another editor
• SMSS Tools (Sql server addin) add-in for Microsoft SQL Server Management Studio
• 7-Zip great archive utility
• Filemenu Tools customise the context menu in Explorer
• Ditto clipboard utility
• AutoHotKey allows you to assign hotkeys to pretty much anything
• WinMerge / DiffMerge differencing and merging tool for Windows
• Linqpad like Notepad but for LINQ
• Paint.net Edit images/Create Icons
• Reflector / dotPeek look inside .net assemblies
• NCrunch an automated parallel continuous testing tool for Visual Studio .NET.
• Teamcity CI made easy
• Octopus Deploy Automated deployment for .NET
• Hangfire An easy way to perform fire-and-forget, delayed and recurring tasks inside ASP.NET applications.
• NimbleText NimbleText is a text manipulation and code generation tool available online or as a free download. It magnifies your ability to perform incredible feats of text and data wrangling.
• mockaroo Web app to generate mock data for testing.
• ShareX Easy screen capture
• FileZillaAn FTP Client

For more dev utilities see Scott Hanselman's post.