Yes, I used to be a regular sending TTM autograph requests. There are many addresses readily available on the net to send to. On a side note, there were a few addresses that I actually dug out for myself, but I DARE NOT give them out as I was asked not to. Mostly actors are very happy to sign and send back, but I've had one or two none replies, one or two strange replies and the odd down and out rude (ish). I'll list a few below.
Jason Wingreen (Boba's original voice) - A lovely man that will reply to everyone and will write pretty much what you request.
Kenny Baker (R2) - Does request payment on his website, but I've always had a reply with just return postage paid. Even includes his own 10x8 now and then.
Jeremy Bulloch (Boba) - Used to sign freely, but would only dedicate (due to eBay sellers). Doesn't sign TTM anymore, but I suspect that if you were to hit him with an email and offer to pay........
Julian Glover (General Veers) - Again, a lovely guy that will sign and return your items.
Frank Henson (Stunts, etc...) - Will sign what you send him and will send a few things of his own for you.
Colin Skeaping (Stunts) - Will sign, but will only dedicate. Again, due to eBay sellers.
Ian Liston (Wes and At-At Driver) - Another good one. Will sign what you send and also include a few of his own.
Michael Carter (Bib) - Will sign and return.
Dermot Crowley (Gen. Madine) - Will sign and return.
Caroline Blakiston - (Mon Mothma) - Will sign and return.
Gerald Home (Tessek) - Will only sign official photographs.
Alan Harris (Bossk) - Lovely man.
Those are just few. There's a ton more..............
Now onto the worth giving a try, not so good and bad.
Ian McDiarmid (Palpatine) - Not known for being a TTM signer, but I have had success with him.
Dave Prowse (Darth) - Don't bother. He sells autos on his website. He used to do a send-in for personal items at a cost, but thats stopped now.
Carrie Fisher (Leia) - Not a big one for TTM, but there have been authentic successes. Does send a lot of secretarials though.
Harrison Ford (Solo) - You will just get a PP sent back.
Mark Hamill (Luke) - No. Just no.
Anthony Daniels (3po) - More chance of Alec Guiness and Peter Cushing.
Denis Lawson (Wedge) - A tough one to call. There was a time that he wouldn't sign Star Wars AT ALL due to an incident that I'd rather not go into. Nothing to do with me. Just to make that clear. He's done a few shows recently and I think he's had his faith restorded in SW fans. I'm not 100%, but I think he may just sign TTM.
Again, the list goes on here, but those are just a few.
A few tips when sending and requesting. DON'T take the piss when sending stuff, such as multiples of the same photo or just tons of photos. Although some of them will sign what you send, others will just return one and you will just end up disappointed. Other than that, it's just courtesy on your behalf really. If it's something that you already have signed by multiple actors, just write and ask if it's OK to send first. That way you know it's safe and will come back. You may have to wait for your reply, but at least you haven't lost that valuable item.
Here's a big one, especially with ones like McDiarmid. Don't bore them with Star Wars. They like to be noted as actors and not characters. Just introduce yourself. Apologise for the intrusion. Explain why you're writing.... You're a fan of their work and tell them what. Tell them that you realise that must be very busy, but could they poossibly spare a few moments to autograph the enclosed photograph for you. It really would mean a great deal to you if they could.
Tell them that you don't wish to take up anymore of their valuable time and you would just like to thank them for taking the time to read you letter.
Don't do what a few have and just send a letter, Dear Mr So an so, would you do me a favour and sign these photos for me. Thanks. As funny as it sounds, it don't go down well.
Oh, and a hand written letter. They know you taken time to actually write to them then. About a page long.
Thats pretty much it for the basics really. If there's anything else you need to know or something about a particular actor, ask and I'll do my best.