eHex

From Shade Tree Programming:

HexEdit is a full-featured binary editor for Windows. It is modeled after the 'binary' edit mode of Microsoft's Visual Studio and offers many of the same features, such as:

• Dual highlighting
• Infinite-step Undo and Redo (even after Save operations)
• Insert and Overwrite for both HEX and ASCII Input

However, HexEdit does not simply reinvent the wheel. HexEdit also offers two significant improvements over Visual Studio's binary editing mode (or, for that matter, most stand-alone binary editors).

• Discrete ASCII and HEX searching
• Intelligent Copy and Paste

Anyone who has ever tried to search for the ASCII string "20" in the binary mode of Visual Studio should appreciate the former. Anyone who has ever tried to copy a sequence of bytes from Visual Studio into engineering documentation or email should appreciate the latter. HexEdit lets you copy byte sequences from text files into a binary file and paste binary data as text into normal text editors.