I used to use UltraEdit-32 back in the day - sadly it's no longer free but when I was using it I found it useful enough that I wouldn't quibble at the $35.00 fee now.
I've heard good things about SciTE which free. It's based on a Linux editor Scintilla. There's a Windows version found at:
http://www.scintilla.org/SciTE.html
Allegedly (though I'm relaying 2nd hand info here so don't hold me to it), it supports intellisense as well as your usual syntax highlighting and code collapsing. I'm not sure if it supports breakpoints and debugging though.
I've been trialing the latest version of PrimalScript which one of my friends recommended to me that I find outstanding, it supports all sorts of neat features - intellisense, . I'm just waiting to find out if the company is going to shell out for it. It's not cheap either though at $279.00. I'd say this app is well worth shelling out for. It supports full script debugging, intellisense, syntax highlighting - the whole caboodle. It also works for a whole bunch of languages, not just VBScript... it does JavaScript, batch files, PowerShell, SQL scripts, the lot. It's a full IDE, not really usable as a replacement for something like Visual Studio but for most single script/file applications, I don't think it can be beat.