Apple just released iOS 8.1 for public with their promising Apple Pay support and bug fixes. Currently we do not have any public jailbreak method for iOS 8 or iOS 8.1 , so it is advised to avoid updating if you have jail-broken device and do not want to loose jailbreak and cydia apps
Cydia Download for iOS 8.1 - Pangu jailbrek for iOS 8
Still we do not have any method to jailbreak or download Cydia on iOS 8 devices. You can have latest updates with Cydia Blog. Pangu team already confirmed they are working for iOS 8 jailbreak , also evasion 8 jailbreak is under developing , its matter of time for release of jailbreak tool. It might come from different name or under PANGU or Evasi0n update.