The official documentation has moved to http://docs.couchdb.org — The transition is not 100% complete, but http://docs.couchdb.org should be seen as having the latest info. In some cases, the wiki still has some more or older info on certain topics inside CouchDB.
If you don't want to use NSURLConnection directly (it's kind of a pain) there are a few Objective-C frameworks to choose from:
Trundle is being used by a few apps already.
CouchCocoa is a newer framework, somewhat higher-level than Trundle. It's supported by Couchbase, but is free and open-source.
CouchObjC is an older project that doesn't seem to be maintained anymore.
If you want to use CouchDB in an iOS app, with a local database, you'll likely want to use the Mobile Couchbase framework.