There are a ton of ukulele tuners available online. Here are some:
This is a great online tuner – you can change it from standard GCEA to other presets. http://www.get-tuned.com/ukulele_tuner.php
Super easy tuner – click on the letter of each string, nice big picture, will only tune GCEA though http://www.dolphinmusic.co.uk/article/2928-online-ukulele-tuner-.html
Ukulele Tabs (a source of a wide variety of songs – chords and some tabs) has an online tuner as well, although currently it appears to be down http://www.ukulele-tabs.com/ukulele-tuner.html
New South Wales’ North Coast Ukulele Collective has one too (as well as a chord finder) – another tuner with a nice big picture, hover your mouse over the letter of each string, will only tune GCEA
http://www.ukulelecollective.com/index.php?option=com_content&task=view&id=16&Itemid=22
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