I usually do online Skype meetings with my team. On my side, it is only me, but on the other side, there are several people with different distances from the laptop (5m radius max).
So far, we have been using the build in MacBook mic, which has very bad sound quality for people farther from it.
I wonder what type/model of mic would help with this situation?
If you are on a budget you might want to give the Blue Microphones Yeti a try. It has switchable pick up patterns on it one of with it polar which will pick up 360 degrees around the mic. It's USB so it should be able to interface with Skype with no problem at all.
I second Mike Rinehart's suggestion of the Blue Yeti. Although I haven't used one personally, it is one of the most popular budget mics on the market. Its switchable pickup pattern means you can set it to capture sound from all directions equally. Interestingly, it actually has three condenser capsules, which allows it to be used in a wide range of applications, and its integrated stand would work very well on a conference table.
However, it sounds like this conference room would not have everyone equidistant from a central microphone, in which case the people that are farthest from the mic might still be quieter enough to make them hard to hear. I'm sure the balance would be much better than the MacBook mics, but still probably not the best. If this is a problem, you might want to go for two or more identical mics, placed such that everyone is nearly equidistant from a mic. I'm not sure how you would be able to configure two separate mic units for a conference call, but I'm pretty sure it can be done.
Of course, another option would be to go with one or more microphones designed for conference calls, which would likely have a similar omnidirectional pickup pattern. Although from a quick search, it looks like a lot of them are equal or greater than the Yeti in price, and since the Yeti is a more well-known and widely acclaimed product, you might prefer going with it.
Many manufacturers make microphones specifically for conferencing that have purpose-designed coverage patterns and low profiles.
An example is a Shure MX396, which can be obtained with several polar patterns, and speaking from experience, works quite well.
Mics made for conferences are a specific application of 'boundary mics.' wikipedia.org: Boundary microphone. These are better for speech intelligibility relative to free-standing mics like the Blue Yeti because (in my personal limited understanding) they eliminate half of the conflicting sound waves arriving at the mic. You have to mount them on a flat surface like a table or wall to get the intended effect. The classic model is the Crown PZM. These mics are condenser mics so they need phantom power.
Basically: none. The microphone in the macbook is not that bad, but if you stand far enough, then it has no way of picking voices rather than other sounds, including the laptop fan, and it will also get some room reverb.
What you need is a proper mixtable and a bunch of mics on table stands.
Mixtable quick search
Note that you need 4 XLR inputs to connect the mics; effects are not your problem, but it's getting hard to find one without. Alternatively, get 2 XLR inputs and make one for the person in charge of the link and the other passing around the table. The USB connectivity allows to use it directly as a soundcard, and the connector is less likely to break than the mini jack -- or worse : the socket.
Mics: I'd go for beta 85 from thomann (T-bone is their in-house brand): http://www.thomann.de/fr/the_tbone_mb85_beta.htm or shure pg 48 : http://www.shure.com/americas/products/microphones/pg-alta/pga48-cardioid-dynamic-vocal-microphone
Quality here doesn't matter much to you, although the heavier the base, the more stable they are, especially with mics mounted (which is the point).
A number of companies make specific products intended for this use case, called speakerphones.
From Wikipedia:
A speakerphone is a telephone with a microphone and loudspeaker provided separately from those in the handset. This device allows multiple persons to participate in a conversation. The loudspeaker broadcasts the voice or voices of those on the other end of the telephone line, while the microphone captures all voices of those using the speakerphone.
Modern day speakerphones connect to your device via USB or Bluetooth, and replace the speaker and microphone in your MacBook with one (or more) microphones and a speaker specifically designed for this purposed. Furthermore they often include DSP algorithms that enhance the speech quality, reduce echo, etc.
Skype tests and certifies speakerphones so it would be advisable to choose a product that have acheived this certification:
Full disclosure: I work for a company that develop audio products and among these, speakerphones.
