As a telecom tech, here's things would interest me:
1. Someplace that offered solutions. Even if they were completely fictitious scenarios, being able to read through case studies of how various hurddles were over come would be great. Perhaps you could get "advertisers" to create solutions that you propose. For example, 'Here's how Avaya was able to meet the needs of the Big Joe's Fish and Chip's chain of restaurants.'
2. Someplace where I can contribute (and get advice!). I just spent 3 weeks trouble shooting an issue with antiquated echo cancellers because the point to point circuit they resided on carried voice, data, and tdd data at the DS/0 level.
3. Editorials and announcements of upcoming technologies and standards. All I can say about that is "Toys!" and if you don't understand, you're not a geek.
4. Similar to both 1 and 3 but subtly different would be a section about "repurposed" technology. Maybe show stories about how developing nations are able to take our aging telecom equipment and provide services to people who have been without. Or, maybe there is some enterprising kid who, oh say, figures out how to unlock iPhones so they can be used with different carriers for example. I find it very interesting to read stories where people make technology do things it wasn't designed to do.
5. A must for any highly technical site is a dictionary of acronyms. My Newton's Telecom Dictionary is getting quite worn out. A wiki would be ok, but I've never found wiki's very readable so...
Depending on the clout of the organization, some free certifications or even just self test would be cool too. Most technical geeks like testing their knowledge, so even just a puzzler or "how would you..." would be cool.
Try hanging out with a few members while they have a beer and see what they talk about. These are the items they contribute to their peers, and these are the types of things they'd likely be interested in online as well.
Hope that helps.