What kinds of things are you doing to make yourselves visible? Here are some more suggestions in addition to the ones already mentioned (I don't know if you do any of these already or not). Forgive me if I'm redundant:
chapter chow - everyone meets at 5:00 on Wednesdays (or whatever day letter day is, so everyone should already be in letters) in the main cafeteria and eats dinner together
dress up day - (Thursdays for us) everyone dresses up and wears their Quill to classes all day
intramurals - do ya'll have intramurals shirts or jerseys that are the same? If you had everyone wearing the same thing it would make your presence known a little better
have a blood drive - team up with another org and have the bloodmobile come to campus. Make LOTS of fliers! This is great because 1-it promotes the Panhellenic spirit, 2-lots of great PR, and 3- you get philanthropy hours and it's for a good cause.
sporting events - does your school have a football team? A basketball team? A baseball team? If you do, make sure everyone attends the games (together) in letters. Arrive and leave as a group. Make banners and place them around campus saying "Alpha Xi backs the (mascot)." Bring posters with you to the games.
realize your potential - the new program is a GREAT opportunity to make yourself visible. Speak with your Programs VP and ask her to do the male/female communications program and team up with a fraternity to do it. Or you can pick another one and team up with a sorority. These programs don't give away any of our secrets and can be adapted for use with non-Alpha Xi's. Also, don't forget about the Askey Grants that are available. You could ask for a grant to bring a speaker to campus to do a program on alcohol awareness or hazing and invite all Greeks and non-Greeks to attend.
letter bags - okay, I know you know what I'm talking about. The white canvas bags with the stitched letters on them? Make everyone in your chapter (okay, you really can't MAKE them, but it's worth a shot) get one and carry their books to class in them. These are really effective.
pajama party/ice cream social - have a pajama party/ice cream social where all the sororities on campus get together and invite non-Greek women to come for a good time (as well as panhellenic info!).
spaghetti dinner - similar to the above suggestion. Have one sorority in charge of the appetizer, one in charge of the entree, one in charge of the desert, etc. Have non-Greek women attend and be "served" by the sorority women.
ETA: I thought of a few more!
newspaper - does your school have a newspaper? Take out an advertisement when you have these blood drives or programs or whatever. Put in an ad after every rush or COB congratulating your new members, then list their names. Also put ads in congratulating the intramurals winners, greek week winners, etc.
radio station - can you get a 10-second spot on your campus radio station? Something like "The XZ chapter of Alpha Xi Delta wants students to back the (mascot). Come to the game Thursday night at 7 pm and be prepared to cheer your team on to victory."
Adopt-a-Highway - self-explanatory. It gets your name on a sign. Just make sure you keep your section of the road clean please.
camp-a-thon/rock-a-thon/swing-a-thon - these are fundraisers that you can do and it gets your name out there. Double bonus.
Keep in mind that COBs and rush are just 2 times in the year when you have formal recruitment so to speak - you are recruiting 365 days a year!!! The more you do for your campus, the more your campus will give back to you.