UkuleleHunt has a huge selection of songs (chords only, tabs, solos) indexed by genre and ease/complexity.
Ukulele Chords King of Charts Ukulele-chords.com is a free chord library offering the largest and the most comprehensive selection of ukulele charts from uke planet.
Chordie Huge database of lyrics and chords. Can configure chord diagrams for ukes in C or D tuning. Can create personal and shared songbooks. Can search by artist or song.
Dominator Ukulele Tabs Good selection of Power Tab, PDF and Midi files for Ukulele
ezFolk.com Good selection of MP3 files, PDF files containing tabs for Ukulele
Richard Gillmans Free Ukulele Tab Links This site provides links to several sites. Richard has done such an amazing job of collecting the links, there is no point in duplicating his effort.
Ukulele Beatles Fun Ukulele chords to Beatles tunes, to learn and enjoy.
Betty Lou Lots of great contemporary and older songs, chords, and midi file. Indexed well, so easy to find stuff.
Live Ukulele Tabs for a variety of songs, pdf files. Intros and outros.
Ukulele Tabs Nice collection of songs (tabbed)
Ukulele Blog Songs on You Tube, and Chords. Great to practice along with. Mainly in French- also has plenty of material in English.
Tab Transposer Copy and paste the content of a tab file or write some chords into the box to transpose
4StringChords You put in a chord, and position, it will show you how to play it . Also, does a look up ... so you indicate the chord shape, and it will tell you the name of the chord. Very configurable, useful for a range of 4 stringed instruments in different tunings.
Ukulele Paradise chord finder, play along songs and plenty of fun stuff
Uketabs - huge library of songs - easy to transpose link
Big Muffin - great selection of lovely arrangements (some with PowerTab, GuitarPro, PDF) some with riffs, solos, intros & outros.
PowerTab - Free, windows only, very widely used
Guitar Pro - reasonably priced. Excellent.
www.gochords.com - authoring, arranging, transposing (check out the site to see all the clever stuff)
http://ukulelejunction.co.uk/ - see iPhone app