Idk about activities, but I know an idea for things you could hand out:

Rainbows represent gay pride, so at the beginning of meetings, hand out Skittles? Or any rainbow-coloured type food. Change the food every so often as to not get boring.

Soz, my idea *shame*

Watch lots of movies. Hang posters

Sorry that this is so long I've had to divide my comment into two blocks of text ^^'
Another thing that might be effective is to have a "description" kind of thing. Maybe you can put it on posters and hang them throughout the school so that others can read them. But it can start of as a first-person description of an average kid, like "I have two older brothers. Dogs are my favorite animal. I'd like to become a doctor or a journalist etc.." then have the final line be something like "And I'm gay". That sort of thing gets people familiar with the description, because the "speaker" is just like them, then they realize that this isn't a person who's sick or needs help- they just happen to be gay.
If you work together with a teacher who might be involved with your group, maybe they can also help you get in touch with a guest speaker who would be willing to come and talk.
Try to introduce the message mildly, espescially if dealing with a religious group of students. Things might back fire if you guys come on too strong.

I also recommend making your primary message one of anti-bullying. Because of religious beliefs, it might be very difficult to show people that being gay isn't wrong. But what can definitely be shown is that discrimination is wrong. I think once people realize that it's not right to be homophobic, acceptance will come on its own. Combine your message with one of anti-bullying and I think you'll be more successful. Unfortunately, a lot of people can't relate to being gay. But I think a lot of people can relate to being bullied. Encourage people to be compassionate and I think the rest will come :)

I agree with the ideas suggested below ^^~
Another thing you could do is maybe form connections with major LGBT support groups. One of them that I blogged about the other day is called "Stonewall". It's a British organization and there website can be found here:
http://www.stonewall.org.uk/
Maybe there's some things on the website that can give you ideas, too.
I think the main message to get out is that LGBT people are exactly that- people. Maybe you can find videos, songs etc. that show that LGBT are just like everyone else. There's some excellent short films on YouTube that aren't ual but get the message across that LGBT bullying and discrimination is wrong.

There's an GS alliance group at my university as well- I unfortunately haven't had the time to join yet, but I'd like to in the future :) Something they did was organize a "day of silence" to raise awareness about LGBT bullying. They posted signs around the campus about it and on the day, everyone involved wore a green shirt and when asked why they weren't talking, they would explain what the cause of the event was. Maybe you guys could make your own shirts and do something similar in your school or community. You can finish the day of silence by having everyone who was involved meet up and you could show videos and discuss the importance of respecting everyone, regardless of their ual orientation.

Stonewall has "Some people are gay. Get over it!" shirts that you guys could base yours off of. There's also "pink shirt day" in Canada, which aims to prevent bullying in general. The back of the pink shirts say:
Today, I have an obligation

No longer will I be silent if you need help

Silence is participation

I refuse to participate in the problem

We're all different, but we all deserve respect

If you need help, come to me

If I think you need help, I'm getting involved

I got your back

You could do something like that and have everyone there "pledge" to stand up against LGBT bullyling.

The person below has some really good ideas. To show your support for the GSA AND LGBTQ community you can hold a fair or do a town walk/ parade. Sprea the word that it's not a crime to love. Cause live has no bouderies. You can make banners, t-shirts, posters, flags, etc and hold a fair for people who accept it. Meetings should be discussing the issue of gay marriages and make it an arguement. Her people who don't understand about the GSA community. Make it well-known to peopl that it isn't a club. A bake-a-thon? Anything to raise money to support the LGBTQ. Well, I cNt give out good ideas... Sorry

Hi! I don't think I've ever actually talked to you, but the topic of this post caught my eye, and I'm super involved in GSA, so, erm, pardon my giant block of text. XD

Depending on your school's location there can be a wide range of activities you can be involved in. For example, my town is pretty big and known as very gay-accepting, so we have a large number of options available, but I'm not really sure what there is available for smaller (or less accepting towns). Even in smaller towns though, there can be plenty to do.

If your town (or a town nearby) has any sort of pride festival, you should see if you can get a booth and have students staff it for the fair. You can get students to design flyers, brochures, and/or buttons and hand them out. You may also want to try checking out any of the small events in your area that may have parades, and talking to organizers about getting a place in them- but be wary of the crowds that will be present. If the area doesn't support gays, you shouldn't force it on them because they will not respond well. You can talk to the people in the Planned Parent organization, as they are well known for being giant supporters of all things civil rights, and can probably help you find activities specific to your area. You can organize fundraisers for LGBTQ organizations, and find out if your state has any basic rights groups that you can have students volunteer for.

However, probably the easiest and more important thing you can do is be involved within your school, specially if there is not a huge acceptance rate. Make sure to be present at all of the club fairs, and school events where club activities are showcased. (Getting GSA shirts and wearing them to school also does not hurt, and it makes reminds the student body of the club.)

And there are a number of other things as well, but I don't want to make this comment too long. Erm... hopefully this helped. ^.^