I love Notepad++, though I use it more for C and C++ than for X/HTML, CSS, PHP, etc. I believe Aptana and Nvu are rather good ones for Web pages. However, KompoZer, a fork of Nvu as Nvu is no longer being developed under the name Nvu (it is now apparently Mozilla Composer?), seems to be gaining some ground. However, I prefer an all-in-one editor and Notepad++ does that for me, not to mention it is lightweight and extensible via plugins. There are others like Notepad2, Programmer's Notepad and another wonderful editor known as SciTE. Those are just a few of the good ones out there... There are more, of course. For example, you can use Eclipse (usually known for Java) via an HTML extension, though the last time I tried it, it was too complex of an interface for me. I'm the type of person that enjoys simplicity.
Whatever you choose, I hope it works for you!