Launchpad currently recommends translating address-book-app in Ubuntu RTM 15.04.

Template "address-book-app" in Ubuntu RTM 15.04 package "address-book-app"

Language Status Untranslated Need review Changed Last Edited By
Cherokee 100.00  100.0% untranslated 100 100 0 0
Dakota 100.00  100.0% untranslated 100 100 0 0
Hawaiian 100.00  100.0% untranslated 100 100 0 0
Inuktitut 100.00  100.0% untranslated 100 100 0 0
Lakota 100.00  100.0% untranslated 100 100 0 0
Ojibwe 100.00  100.0% untranslated 100 100 0 0
Spanish 000.00  100.0% translated 0 0 0 2016-06-01 16:09:48 UTC 2016-06-01 Víctor R. Ruiz
Tlingit 100.00  100.0% untranslated 100 100 0 0
Yiddish 100.00  100.0% untranslated 100 100 0 0
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Key to this table: “Unchanged” means Translated
and “untranslated” means just that, Untranslated

Other versions of address-book-app in Ubuntu RTM