Psst! Winifred--over here. DaniGirl hasn't been on the site in over a year, so she's not going to see your advice.
Hahaha! I saw this thread earlier and was going to comment until I saw the dates and I figured I'd let it die.
But since it's "necro'd" anyway and some writers might see it and have the same question as the long departed DaniGirl, I thought I'd throw my 2 cents in.
The answer to which agents in L.A. accept email queries is ALL and NONE.
No agent WANTS to get queried (or read anything), but they are ALL looking for the next great piece of material. Few reps (agent or manager) of any prominence will say they accept unsolicited submissions as they don't want to get bombarded with a million queries. That being said, nearly all of them receive dozens of queries a week and, on occasion, do request to read a handful of scripts based on "unsolicited" queries.
My best advice is to seek out literary managers (instead of agents who generally have too many clients to read a lot of material based on queries) and query the managers instead. Managers have fewer clients and tend to focus more on building a writer's career as opposed to primarily selling material and securing jobs for clients (as agents spend most of their time doing).
Query tips:
1) Keep it simple. Only a few sentences. Do NOT give them your life story or a whole synopsis of your script.
2) It's all about the logline -- the one or two sentence logline is really all they're interested in. If they are intrigued by it, they might request a read. It really is as simple as that.
3) If you can personalize the email to them, in a quick/simple way, it might make them more inclined to read on. They can tell if you're just cutting and pasting the email to 1,000 different reps and those types of generic queries are less appealing.
4) KEEP IT SIMPLE. Really it's mostly about the logline. If they don't love your logline, they're highly unlikely to request the script regardless of whatever else you add in your query. And the more information you cram into your email, the more likely they are to just hit delete since they don't have time to read a wall of text.
5) Do NOT harass the agent/manager. If they do not respond to your query, do not query again with the same screenplay/logline. If they request a read and you send the script, do not keep asking them if they've read it yet. It's a small industry and you don't want to get a bad rep. Fire and forget. If they're interested, they WILL contact you.
6) A great way to get the interest of reps is to enter and win (or at least be a finalist) in a prominent screenplay competition - like the Nicholl, Austin, PAGE, etc. If you do, then the managers and agents will likely contact YOU and you won't have to query them at all.
My advice comes from working at an agency and interviewing dozens of agents/managers for my podcast and website.
Good luck to all you screenwriters looking for representation!