We are using GoToMyPC. The other one we looked at was LogMeIn. They are expensive (over $300 annually although I can't remember the exact amount) and there are cheaper ones out there. I read somewhere that GoToMyPC and LogMeIn are owned by the same company so I'm not sure why the pricing is different.
If you do a search for other software then use the terms "remote access software." There are some programs with a lot of bells and whistles but those are for corporate use. Look for the ones that are for 1:1 use or where the use is by the family tech geek who is bailing out the other family members. Some of the programs have a free trial period with no commitment to buy so if you get your timing right then you could conceivably use the software for a one week or one month free trial, make sure your mom is set and then cancel.
I went with the one that I figured he would find easiest to respond to when I need to come in. It has been a game-changer though in his quality of life and my sanity so the cost is completely worth it in my mind, especially because he is in an independent living facility and they are on lock-down right now. This is how he is keeping in touch. The other day I had to buy a new printer for him. It was delivered to his facility, the staff brought it to his unit out of the box and then plugged it in. I was able to log in and make sure it worked properly after he turned it on (

) so now he is happily zooming and printing and staying active with his friends online. I am sure FaceBook has seen a huge upsurge in use now that he is posting and trying to friend every person he has ever known!