Here is a site that may be of interest:
http://www.playukulelebyear.com/
I discovered this by going back through the UkeTalk forum pages from the beginning. I am about halfway through them now and have found out about a number of really good books and a few sites, with Jim D'Ville's being a goldmine. He has a series of 26 videos for beginning players (such as me) on Youtube and a series of 4 DVDs (also available as download) that constitute his workshop on playing by ear.
Then, in addition to these, there is another "by ear" video called "Hear the Strum" at
http://www.musiclessonsvancouver.com/page6/page6.html. The idea in this video (DVD or download) is that instead of trying to memorize a bunch of strums as "down down up down ...", you learn to FEEL the rhythm of the music and strum with it as you hear and feel it.
I am working through these at the moment. I think the cost is very reasonable for what you are getting. We each have at least slightly different learning styles and ways of taking in information. For some, taking lessons either in person or via Skype is the way to go. For others, this series of videos/DVDs is the way to go. For others, books and other DVDs might be a good path. I suspect that for most of us, some combination is a workable solution.
There is a lot of good information to be had by going back through the UkeTalk sub forum, especially the earlier pages. I found one post by seeso (is he still around?) that I printed and laminated for reference. It gave a very concise example and description of coming up with a short musical phrase (motif) and developing it into a longer piece as a means of composition. There are some real gems in those pages.
I have also just "googled" for various ukulele related subjects. The best thing I found for me at this stage was a list of relatively simple two and three chord songs. The list consists of the titles and the letter of the first note of the tune as it fits nicely on the ukulele. This is great for daily exercise picking out the melody and chords of tunes for ear training on the ukulele.
Two books that were mentioned in the UkeTalk pages that I am finding particularly helpful are:
The Natural Way To Music (you can get the accompanying CDROM as a separate item) by Jim D'Ville and Bill Keith (the famous banjo player):
http://www.beaconbanjo.com/product/music-etc/the-natural-way-to-music-wcd-rom/.
Understanding Ukulele Chords by Robert van Renesse. This is a Mel Bay publication, so it should be easily available. This book is very well laid out, with each page being a lesson. The book teaches most everything you need to know about understand how chords work in music and how to create them on the ukulele, all in bite-sized lessons that are easy to assimilate.
I hope this information is helpful at least to some reading here. Not all information is useful to everybody, but it is definitely worth a look to see if some of it may be useful to you. The books and DVDs discussed in this post are really foundational to whatever music and styles any of us learning to play the ukulele are interested in.
Edit: I forgot to mention what is really probably the most important part of all this - two "fakebooks" by Liz and Jim Beloff:
The Daily Ukulele and the leap year edition of The Daily Ukulele
From what I have read, these seem to be the standard books for ukulele jam sessions of various types. They are certainly a good way to both check your "by ear" efforts and as a starting point if you want to arrange tunes in whatever style you want to play them, as well as for strumming and singing. In other words, these are great collections for any ukulele player.
None of the information in my post is new, and is probably "old hat" to those who have been playing for even a few months. But sometimes it is good to post this information as earlier posts scroll off into the archive pages, where one must search to find the information.
Tony