The support of locking will be preferred.
Windows Explorer itself is a WebDAV client. Don't know if it supports locking though.
Since you want locking, that really narrows it down a lot. From some searching I have only found one windows client that looks fairly good + supports locking. It's commercial ($59) but they offer a trial version: Bit Kinex
If you don't require locking you can look at WebDAV.org's project overview:
Total Commander with plug-in http://ghisler.fileburst.com/fsplugins/webdav.zip supports webdav.
"Windows Explorer itself is a WebDAV client."
Yes, but Vista requieres update
There are also some cases when WebDAV is correctly configured under Windows Explorer, but it does not want to work properly.
Explorer's built-in WebDAV client can be excruciatingly slow so I use a separate application called WebDrive.
WebDrive creates a mapped network drive for each share you open so you can access shares from any Windows app transparently. Best of all, WebDrive also supports FTP, SFTP, and Amazon's S3 so you can use it for pretty much any remote network location. I bought my copy for WebDAV but it's become my default SFTP client.
Oh, and yes, WebDrive does support locking for WebDAV shares. (And 64-bit if you're running an x64 install.)
The only downside is that WebDrive is a commercial product. It's $59.95 with one year of updates or $79.95 for two years of updates. Each license grants perpetual use of the product; you just pay extra for an extension to the update period. It does have a 20-day trial, though, so you can try it out for a while and see if you like it before putting down any money.
I find CrossFTP Pro is a reliable WebDav client. It also supports multi-tabs, multi-threads, locks, proxies, etc. It has a 30-day free trial so you can try it out first.
I have found and started using EngInSite DataFreeway which is a freeware program for Microsoft Windows.
[DataFreeway - free SSH (SSH1, SSH2, SFTP), WebDAV, FTP GUI Client for Windows]
I have only used the application for a couple of days, but it has been working pretty well so far. Like any software read carefully through your licensing agreements. Whoops, forgot about the locking part, not so sure on that one.
For those of you trying to get WebDAV to work, here is a decent client troubleshooting link for Microsoft WebDAV client: http://www.webdavsystem.com/server/documentation/troubleshooting.
I must say, the more I dig into this the more I learn how poor Microsoft supports WebDAV web folders.
Note:
For those of you having trouble accessing web_dav from Windows XP try using the port number in the url when setting up the new network place. E.g. http://mydomain.com:80/foo worked like a charm for me.
I agree: this could be very powerful but support for WebDAV in Windows (XP, Vista, 7) is poor. It feels very buggy to me.
Novell Netdrive is a very good client, one of the oldest and probably one of the best ones. http://www.sitepoint.com/blogs/2004/10/03/novell-netdrive-webdav-client-for-windows/ It is not free either but you can find many copies on the web by googling for it, as it is part of the Netware CD and provided by many universities (who have a netware licence) for their users.
Dare I say it, and albeit too late, but Adobe Dreamweaver is an expensive but decent option.
It supports locking and version control.
DW also doesn't change that much, so if you can find an old copy you'll be almost as golden as with the newest version - though being able to set up multiple servers and testing servers for a single 'site' is really handy.
Many thanks for all these links. I've been testing BitKinex and found it pretty useful. There are 2 things I'm still missing: 1.) I'd like to see the different file versions via properties or so... 2.) Is there any easy way to send a file (by URL), so that people without User-ID can edit this file and return it to the WebDAV container? BR