It depends on your state and I wouldn't encourage you to share that info because that's a lot to put out there on the internet for everyone to see.

Anarchist orgs are fragmented and often quite sporadic in their organisation efforts here. If you're on the east coast in a major city then there's probably an anarchist bookstore or venue (e.g. Cafe Gummo). Otherwise seek out your local IWW chapter or Food Not Bombs. Failing that, your next best bet would be to look for local antifascist orgs or irl anarchist book clubs because you'll likely find your local anarchists there.

For MLs you have the CPA, ACP, and CPA-ML.

The CPA-ML is essentially an underground org so if you're not a part of it then you won't know what's going on with it and if you're a part of it then you aren't telling people what's going on with it.

Numbers are suspected of being pretty low in this party. You'll likely see them attending major protests and similar events with two members at a stall because they have a designated number of members who are publicly associated with the front-facing part of the org. If you're interested in the org, I'd speak to them when you see them.

The CPA is the longest-running communist party in Australia. Well, technically speaking anyway. It's a convoluted history but they're essentially the heirs to the old CPA after splits and party renames and liquidation and all kinds of bullshit. I can elaborate on this if you're interested but tbh it's largely a matter of historical curiosity and it's inconsequential to your question.

The CPA is the largest ML org in Australia.

The ACP is the newest ML party in Australia and it recently split from the ACP over the establishment of the Community Union Defence League.

The younger members of the CPA tended to go to with the ACP at the time of the split.

There aren't branches of the ACP in every state yet, at least as far as I'm aware.

There's significant divergence between the lines of each ML party in Australia and I'm not going to summarise them because I think that's not really fair for me to do - I think it's better to do your own investigation into each party's line and their rationale for their positions.

Ultimately I guess it depends on what your priorities are as a prospective party member as well. The CPA-ML is small and it's activities are clandestine so it's hard to say much about that. The CPA is the largest party and they are more prominent in protests. The ACP is smaller, less prominent in protests, but much more active in the community.

Keep in mind that although each party adheres to democratic centralism, there will be divergences in opinion within the party on matters (or, at least there should be in a healthy party). Seeking out the party whose opinions align perfectly with yours is kinda a lib attitude imo because every party is going to have the wrong take on issues some of the time and it's about a movement rather than picking out which organisation which you find to be the most flattering for yourself, if that makes sense. I think what's more important is how the party manages to correct course, how it handles dissent internally, and ultimately how vital the party itself is.

You can have a massive party that achieves nothing because it doesn't organise any actions or which takes the wrong line because it doesn't have a strong focus on ideological development of its party members.

You can have a strong, active party that doesn't handle dissent within the party properly and it will invariably end up in ruin because the party leadership will steer it off a cliff or it will cut itself off from the masses/the majority of party members sooner or later.

You can have the perfect ideological alignment or maybe even an ideologically immaculate party which doesn't achieve shit because in reality it's just a glorified book club that doesn't put any theory into practice.

I guess my advice for you is to find which party is the best fit for you in terms of culture (e.g. the basic stuff that is important for you - for example, I'm queer and multiply-neurodivergent I'm not going to fit into an org that is hostile or lukewarm towards queer or neurodivergent people. Your priorities might differ but I'm sure you catch my drift.) then see if it's a party which brings in new members readily and which has a healthy system of management internally (e.g. how it works on the ideological development of its party members, how it manages dissenting opinions, how it corrects party lines when they have proven to be the wrong ones etc.) and that has strong links to the community.

For the sake of declaring bias, I am an ML and a fellow traveller of the IWW and the ACP but I was not involved in the CPA/ACP split and I am not a member of any party due to poor health so I contribute sporadically to the efforts that are most important to me when I am able to but I'm not really capable of being a committed party member of any org presently.