+7  A: 

Unfortunately, the best thing I have seen is the jquery.combobox, but it doesn't really look like something I'd really want to use in my web applications. I think there are some usability issues with this control, but as a user I don't think I'd know to start typing for the dropdownlist to turn into a textbox.

I much prefer the Combo Dropdown Box, but it still has some features that I'd want and it's still in alpha. The only think I don't like about this other than its being alpha... is that once I type in the combobox, the original dropdownlist items disappear. However, maybe there is a setting for this... or maybe it could be added fairly easily.

Those are the only two options that I know of. Good luck in your search. I'd love to hear if you find one or if the second option works out for you.

Elijah Manor
+5  A: 

For large datasets, how about JQuery UI Autocomplete, which is basically the "official" version of Jorn Zaeferrer's Autocomplete plugin?

I also wrote a straight JQuery combobox plugin that's gotten pretty good feedback from its users. It's explicitly not meant for large datasets though; I figure that if you want something that prunes the list based on what the user types, you're better off with Jorn's autocompletion plugin.

+20  A: 

Here's one that looks very promising. It's a true combo - you see what you type. Has a cool feature I haven't seen elsewhere: paging results.

FlexBox

GeorgeBarker
Nice, thank you!
splattne
I will second the FlexBox recommendation. It is has a very, umm, flexible styling and UI options.
Ben Griswold
New version (0.9.3) just released. FlexBox now supports client-side JSON filtering.
Noah Heldman
+6  A: 

This is also promising:

JQuery Drop-Down Combo Box on simpletutorials.com

Anthony Kong
+2  A: 

Why don't you try http://jqueryajax.codeplex.com/. It is a collection of ASP.NET controls that contains multicolumn drop down as well.

+4  A: 

An official jQuery UI ComboBox/Autocomplete component is in the making... (previously in beta for jQuery UI 1.5.x), see jQuery UI Wiki

Sander Versluys
This is now live with jQuery 1.8. I'm using it quite successfully, it's been a well designed widget.
Boldewyn
Are you guys experiencing the post effect? When I click the arrow to toggle the list, my page is posted and I get a page refresh...
Keith
+9  A: 

Another nice plugin is Sexy Combo

br1
+1  A: 

Activewidgets has a very nice looking one. No idea how well it performs on large datasets. http://www.activewidgets.com/ui.combo/

Erik Haugsjaa
A: 

I had the same problem, so I ended up making my own.

It has a template system built in, so you can make the results look like anything you want. Works on all major browsers and accepts arrays & json objects. http://code.google.com/p/custom-combobox/

Donny V.
+1  A: 

I found this other one: http://code.google.com/p/jquery-jec/

Also seems like a good option.

Hugo
Must second this recommendation. Does precisely what is supposed to do i.e turn a select-box into a combobox. Comes with methods that allow it to work with dynamically populated select-boxes.
RisingSun
A: 

A new fork of the sexy-combo project is now out which looks promising: http://code.google.com/p/ufd/

lomaxx
A: 

Hi,

I'm looking for the same. The one I liked most till now is this one for ExtJs - except I havent tested it with large Lists: www.sencha.com/deploy/dev/examples/form/combos.html

Here is another really(!) fast one: http://jsearchdropdown.sourceforge.net/

For example the SexyCombo works quite fantastic but is way to slow for longer lists. The SexyCombo folk UFD is a lot faster, but initialization time is still quite slow for really huge lists. Besides I get sometimes some little! "flashing". But I guess there will be some updates in the near future.

Sithlord
+1  A: 

Hi,

Here's a really cool one: http://www.xnodesystems.com/ The Dynamic List Field not only has the autocomplete capability, but also is able to do validation.

Richard Xiong