With all the different new means of contacting us (IMs, emails, phone, etc.), how do I determine which agents hould handle which kinds of contacts? I'd like to think that all my people were equally skilled in all areas, but that's just not the case. Any suggestions for balancing knowledge and a particular knack for a particular medium?

This is an interesting question. If you would consider only the phone media, than the employees with a less number of the skills should get the inbound calls first just for the efficiency reasons. When it comes to the mix of different medias things are getting far more complicated. I guess there is no single best way to combine medias but there are several strategies and the choice depends on the mission and vision of the contact centre. Somehow I have an idea that employees would prefer to work a full day only on one of the medias but have slight media rotation during the week. From the speed of answer reason you could prefer to set employees on email or internet if the phone media on that day is overstaffed.
I would say, while making these choices and making the roster think broader and consider different interest in the organization, facilities to schedule and monitor the activities and your mission and the vision.

Communication styles that work well over the phone can quickly be misinterpreted over an e-mail. The most effective environment I worked in with all communication styles broke out phone and non-phone environments. However, separate testing for phone and text (e-mail and chat) environments focusing on things like grammar, spelling, and courtesy will greatly improve the customer contact.

I found that some individuals who had the voice tone of a rock did very well on e-mail if they had the needed attention to detail. As well others that struggled to meet the productivity criteria on text were still able to articulate very well verbally with customers.

So I say (as long as it's financial feasible) - divide and conquer.

My suggestions is to allow each of your employees to have access to as many different communication tools as possible. Users will gravitate to the ones they are more comfortable with. I would just be careful not to allow users to have access to those which there is NO business need.

With respect to IM, unlike email, it doesn't currently sync with CRM systems. If you are interested in allowing it, and having all IM chat link back to the CRM system I would be interested in hearing about it. We are currently engaged in a project to do just that - and since you mentioned IM, I am curious as to how you plan to bring all of your CRM data (and communications related to customers accounts) into the system.

Going back to the question about what works best, I believe it's about taking measurements on the communication tools you use and figure out what works best for what type of interaction. If I were to get specific based on experience, here is an example of how I might organize to come to categorization for measurement:

Sales Interactions communications means consist of:
Face-to-Face Meetings:
Phone:
Conference Calls
Email:
Requests for information from the customer
Providing information to the customer
IM:
Blogs:
Website:
Social Network sites:

In a perfect world, I would then make sure I capture these categories in the SFA tool in a way I could report on. My goal would be to report on which activities and/or combo of these activities drive the most sales in the shortest time span. I would find out which sales people use those the most and why. Then, if I have the budget, I would look to find out from a research firm to find out in my industry based on the products/services I sell what customers prefer, then implement a process incorporating the best communication tools with the expectation I will need to revisit this bi-annually since the technology changes so quickly.