This is a list of tools that will make it easier to customize Indexhibit. Taking into account that Indexhibit is free to use, I list here only some free tools I either use regularly or know of. There are many more, just an internet search away...

FTP clients

Three popular choices: FireFTP (Firefox add-on), Cyberduck (Mac) and FileZilla (Windows/Linux)

Code editors

If you are customizing Indexhibit you will need to edit, at the very least, a stylesheet (CSS). Using a wysiwyg editor like Dreamweaver or a word processor like Word is not a good idea unless you know what you are doing. And anyway there are many good free dedicated code editors for all platforms:

Linux, Mac and Windows: Bluefish, Komodo Edit, Aptana Studio, Eclipse, jEdit
Windows only: Notepad++, HTML-Kit, Scriptly, PSPad, HateML Pro
Linux only: Quanta PLus
Mac only: I couldn't find many Mac-only free source-code editors. Text Wrangler appears to be the only one, unless you want to go for Coda, which is excellent but not free

and many more

and last, for the hardcore experience, there's always Vim (Linux), gVim and gVim Portable (Win) or MacVim (Mac), and the grandmother of them all: EMacs

Browser developer tools

All major browsers have some kind of developer tools, either in the basic package or as add-ons. At the very least you want to know what's happening under the hood: View Source/Ctrl-u and Firebug (a Firefox add-on) are your friends

Reference library

An excellent reference and learning tool: W3Schools, and it also has validation tools and a color picker