The current most active chatrooms right now are Placebo and WSS. I also recommend R_chat which is new. Abyss is also decent but less active.
Active chatrooms:
Placebo ------------ http://placebordtyjrxo3mmlfg5i4mwsotzguplvblb6b775gs2x7lnftfrid.onion/
WSS Chat ------------ http://wsssspmmqsmqarsjxe643rkfafirnxxx3gffcygyxz3k57h6beudstad.onion/
Kiwi-IRC ------------ http://34vnln24rlakgbk6gpityvljieayyw7q4bhdbbgs6zp2v5nbh345zgad.onion/webchat/
Abyss ------------ http://forwhoallvglhpsx6dhycfb4fu4a2lqkvxtwlivruw765qxofyns7wqd.onion/
R_Chat ------------ http://rchatxpcq3n5wgkhxdccg2a575ozthnqr3d2k5mewlkaoddmffmpiqqd.onion/
TWS ------------ http://twssssggaixqajfh7e5gqczxjdd4reydgjtysh2ifksutaa766yxfdqd.onion/ ------------ less active -------- new chat
404 chat ------------ http://4o4o4hn4hsujpnbsso7tqigujuokafxys62thulbk2k3mf46vq22qfqd.onion/ ------------ less active
Dark forest ------------- http://dkforestseeaaq2dqz2uflmlsybvnq2irzn4ygyvu53oazyorednviid.onion/ ------------ less active
Red chat ------------- http://3bu5sy446zbvqugbomvulx4ev43s2tgqcilvsg5oqlvguuziutljzgad.onion/ ------------- less active --------(cheap le-chat)
- - - Chats experiencing downtime or shut down - - -
The onion Parlor ------------ http://topvnbilp2oo3mcyurmgszhsadhshlct4czmaas5t4h3iegkqkuiskad.onion/
The end ------------ http://theendgtso35ir6ngdtyhgtjhhbbprmkzl74gt5nyeu3ocr34sfa67yd.onion/
bhc Black Hat Chat:(http://blkhatjxlrvc5aevqzz5t6kxldayog6jlx5h7glnu44euzongl4fh5ad.onion/ ------------ (cheap le-chat)
Breach null ------------ http://nullzifixlsswy3iz2amgznismgvxvj3zxec3quod7uc4ro2duiw6zqd.onion/ ------------ (cheap le-chat)
***I NEITHER ENDORSE NOR APPROVE OF ANY CONTENT OR CONVERSATION WITHIN THESE CHATROOMS, AND I MAINTAIN NO AFFILIATIONS WITH "ANY" OF THEM. ***
I'm using a Tails OS - I'm trying to create an account in Placebo if that helps.