I'm using PSPad text and code editor.
It's a freeware and capable of plain text editing (spellchecker included) and HTML coding. It also makes a simple yet powerful IDE - PSPad catches and parses compiler output, integrates external help files, compares versions and so on... Here is a screenshot.
There are a couple less features than the version that sells for $799 (Pro) in the US. But you can still get most of those features if you use another good, free, open source, IDE written in C# - #Develop. SharpDevelop @ic#code
Despite its name, it works with almost all .Net languages (VB.net, C#, C++.net, Boo, etc)