Several things I've done in the past is going straight to the heart of whatever the site's focal point is. In this case, MLP:FiM is the fandom. Opening some sort of online store selling MLP-related merchandise, as well as MLP Forums branded paraphernalia may be expensive to start up, but would ultimately have a positive affect on the site.
Other possible solutions might be offering some sort of solution. You have server space, correct? Why not incorporate that into the MLP Forums brand? Work it in as a feature to the site, where a user might be able to purchase a "room" of some sort where they may do what they please. The possibilities there are endless. On other forums, I've run something called "Teams" which is a site-wide roleplay where users join teams and battle for control of specified forums. It's really fun and gives users a more intimate feel for the site, but also plays into monetization; the teams rely heavily on financial support, and buying some sort of currency gets them weapons, forum space, etc.
Whether it be some sort of forum-integrated approach, a store, a service, or something else, donations won't support us for long, and advertisements still don't seem worth it. Just my opinions.
Incidentally, I've been developing both of those ideas. Great minds think alike.

IPS have an add-on called IP.Nexus which is essentially the ultimate site monetization tool. It can do everything from managing an inventory of physical items, keeping track of shipments, and selling ad space to automating the sale of hosting accounts, a support ticket system, and a heck of a lot more. You can check out the full feature list here:
http://www.invisionp...products/nexus/Selling MLP Forums t-shirts
has been suggested in the feedback forum before, and it could feasibly be done with the help of an artist or two. It would be really cool to create a marketplace for pony merchandise in general as well (although I'm not sure what legal formalities may be involved with that - I might need to seek a license from Hasbro, for all I know).
Hosting is something I already provide, albeit it's a rather low-key service with very few (but very satisfied) clients, two of whom are members of this forum. The idea of growing some kind of fully-fledged hosting operation out of MLP Forums is one I have been turning over for quite a while. With IP.Nexus, it could be integrated directly into the forums.
Let's get us some EqD publicity.
In my state, I'm just a few whiles short of a credit card; sadly I cannot donate (or order anything off amazon...) But I'd hope to think that any pony-community; no matter who it's run by, what it's about, or when it started; would hate to see another die. This is my last hope for humanity, and yes, it is ponies.
I'm running the opt-in ads, and click the ones I have an interest in. I shamelessly promote these forums on random communities I'm on, pony or not. I may not be contributing much, but it's all I can do for now. 
Don't get the wrong idea - we're not "dying". Not even close to it. But this particular server move is a proactive measure we are taking now to make sure our hosting doesn't buckle under the stress it will no doubt receive in the coming months. Those of you who joined last year may remember how many times we crashed the past servers we had been on, and it wasn't fun for anyone. With this new dedicated server, resource issues will be a thing of the past.
I really appreciate what you're doing, Fghik, to actively contribute to the community and try to keep new members coming to it. Having ads on helps as well. You might not think that just your opting into ads makes much of a difference; but it's something else when hundreds of members do.
While you are not making a direct monetary donation to the site, you are very much supporting it in other ways that are not necessarily any less important. Thank you.