Our Alliances update is now live, adding new communication features to the site for guilds who are in Alliances!
To create an Alliance, you would login to your Site Admin and go to the Alliances tab, then click "Add New Alliance"; a popup will be shown asking you to type the url to the site you wish to ally with, auto complete will help you to find the site you are looking for:

One you have selected the site, a Pending alliance will be listed in your Site Admin, awaiting the approval of the other site. Once the other site approves the Alliance it will then be active.
Features of an AllianceWith an active alliance, members from your site can login to theirs, and members from their site can login to yours. Alliance members belong to a new limited account type, "Alliance", which you can configure in the Permissions tab, and belong to a new view level, "Alliance", you can use to control what forum/poll content they can see.
Who's OnlineThe Who's Online block has been updated to include Alliance members. Alliance members display similar to your regular members, except clicking their name will take you to their profile on their guild site, and the color of their name can be configured to be different in the Theme Editor. (in the example screenshots Allied members have been set to Green, while regular members are Pink)
Event SignupsAlliance members can signup to Participation events on your site, allowing you to plan events with your Alliance and see who can show up from all of the guilds within the alliance.
Private MessagingPrivate Messages can be sent and received from Alliance members. Your inbox works as a global inbox, so you do not need to login to an Allied site to see private messages from them, you can just login to your own site and will see any pms you have; and you can send PMs to allies from there as well.
ForumsForums can now be shared among alliances. Any forum category or forum thread set to the "Alliance" view level will be available to your alliance members. Forum Categories/Threads set to Member will be restricted to your Guild Members only.
*note: Previously the default view levels for forums were Guest for viewing, and Member for writing. This has now been updated to Guest for viewing, and Alliance for writing. This is because if you are not in an Alliance, Alliance and Member are the same thing; and if you are in an Alliance, you typically will want to allow participation from your Alliance on most forums, with only certain ones limited (which you can do by setting those to Member or higher View Level).PollsAlliance members can now vote on your polls. You can restrict what polls they may access by setting a view level higher then Alliance to the poll.
ShoutboxAlliance members can now post on your shoutbox, allowing for some quick chatting between sites.
All of the Above is OptionalAll of the above permissions for Alliances are optional. You can configure what your Alliance members are allowed to do on your site in the Permissions tab of your Site Admin. If you do not want Alliance members to be able to use the Shoutbox, it can be turned off for them, same with the other features.
Alliance Color Configurable In Theme EditorYou can set the color for Alliance Members to show up on your site in the Theme Editor; by default it is the same as your Member Links. If you open the Theme Editor you will see there is an "Ally" link you can click to set a color for. Severed Pinkies will be going through all of her themes today to update them to have separate colors for Members and Alliance members, so if you are using one of her themes you can just re-apply them.
With the Alliances update live, we are now focusing on several small fixes for a week or two, which includes the Meta tags as we have had several members request it, so this is coming very shortly to the site =)
Keep up the good work you guys.
Guild sites may only be allied with other MMO Guildsites guilds; MMO Fansites is a completely separate site and not really tailored to support guild features (it does not have the guild alliances feature built into it). =)
Cheers,