For years I've used a great freeware tool, FileLocator Lite (formerly known as Agent Ransack ), and I (as well nearly everyone I show it to) love FLL for several reasons. Beyond fast, effective, and easy searching, it also has a cool regular expression building wizard that may be reason enough to use the tool when you need to create a RegEx quickly. It's the freeware version of a commercial product, File Locator Pro, and can be found at www.mythicsoft.com/filelocatorlite/.
(Update in 2010: Originally, the free version was only packaged under the name AgentRansack, which was a little scary-sounding for some tastes. The makers finally offered a rebranding of the tool under the name File Locator Lite, though they still also offer it as AgentRansack, being the same product. The makers just seem to have a fondness for the "old" name so are going with both.)
(Update in 2013: While I still most highly recommend FLL, I do want to add that if you're ONLY searching for files or folders by name, not content, there is a potentially better tool to consider. See the added section at the end of this entry.)
BTW, I do realize that the Windows File Find feature can be enhanced by using its available Indexing Service. I've never been a fan of that for various reasons, and many won't enable such (for good reason) on production servers. Yet you may need to search for files on such a server. This tool can do it with little overhead. And I realize also that later versions of Windows do offer better text file searching, but it's still not as simple as it could be (if the first search doesn't find files, you're offered a chance to do a deeper search). This tool is incredibly simple to use.
Sadly, some people may not ever do searching for files by name or content (or suffer productivity) simply because the available tools are so poor. This one will change your mind!
Definitely favored over other search tools/editors
Since learning of it in about 2004, I no longer use the find feature within editors like Eclipse, DreamWeaver, CF Studio, or various notepad alternatives to search across multiple folders anymore. AgentRansack is so much faster than those in my experience, whether searching tens, hundreds, thousands, or even hundreds of thousands of files. (I've even used it to search millions of files and it did not take hours to do the search.)
And when compared to the Windows File Search feature, it's not only far faster but also DOES search for content in ALL file types. Have you ever used Windows find to search text in CFM files, and found that it never finds files you know it should? The problem is that it has an internal list of file types it will search, and all others it will simply ignore. It also ignores files marked with the hidden and system attributes, which may not be expected. (By Windows Find I'm referring to the feature available from the Start menu or via WindowsKey-F).
And unlike using your editor to search, it doesn't lock up your editor while it's searching away. And even then, it's really FAST! I find it can search gigs of content in just a few moments--yet it DOES NOT rely on indexing the content in any way.
Another great benefit it has over the other more traditional search approaches is that while the left pane is showing the files it found in its search, a right pane shows (for any file you select on the left) the lines WITHIN the file that matched the search. Yes, in some other search tools the search results pane allows you to click a result to open the given file at the given location where the search result was found, but this approach in AR is just much simpler and more effective, I think.
Perhaps most powerful, it also integrates with the Windows Explorer interface, so it's easily reached by a right-click on any folder to search that folder and its children.
Bonus Regex Feature
As I hinted above, beyond searching, AR is also great for its really nifty regular expression feature, to help build regex's declaratively (with a wizard-like interface). I find myself opening it just to create a RegEx when needed. More than that, there is also a useful "test" menu option where you can enter a RegEx, and some text against which to search, and it will show what the regex would find in that text. Very handy.
Check it out
Everyone I've shown it to has been impressed. Check it out.
You can see screenshots of 3 main parts of the interface in use (including the regex wizard and results viewing aspect) at the site.
I should also mention that this is indeed just one of dozens of such file/find tools that exist, for Windows, *nix, etc. (yes, including grep tools for both OS's). I do list dozens more in a category for these tools at my CF411 site, which lists over a thousand tools and resources of interest to CFers.
One more update
Here's one more update I'd like to make: if you may be searching ONLY for files (or folders) by name and NOT by file content, then there's a still-better free tool for Windows that I'd recommend: Ultrasearch, from jam-software.com, the same people who make the also excellent and powerful TreeSize tool for analyzing your disk space usage, per folder.