My son is 9 years old and we have been homeschooling him for three years now. This year, he doesn't have any friends. Previously we lived in the UNM Student Family Housing where there were tons of kids for him to play with. Once his father graduated, we bought a house in Rio Rancho and left all of his friends behind. This year, his sister started kindergarten in public school, which means he is left without any kids to play with.

Can anyone suggest any activities for him to attend to meet other homeschooled kids?

Hi sunflower!

Have you checked out AHEC?   http://www.homeschoolravens.com/  (They have some satellite programs on the westside)
Have you checked out Rio Grande Homeschoolers?   http://riograndehomeschoolers.com/forum/phpbb/viewtopic.php?f=6&t=117
     (great!  I see you have . . . awesome!)

There are probably will be some westside families who respond to your threads . . . what a great idea to post!
Great to meet you and sending you LOTS of support & love . . . our son is about the same age and I know you'll find some great activities for him.

We find ourselves driving & commuting with most of our activities - if you're able to, I'd encourage you to consider membership into multiple groups to support him.
(Including this group, too . . . you'll find many commute-worthy programs & classes going on . . . they're fabulous)
It's a great way of "feeling the pulse of the city" and there is no longer that illegitimate, immature "taboo" there used to be concerning membership into many groups.
Join away - feel out all the wonderful opportunities for him!  :D  ABQ is a great place to grow within