Hopefully we can make this place a nice listing of mobile routers and portable modems that are known to work with IRLP. While not an official topic relating to IRLP it is a frequent discussion on the boards. I have taken the liberty of scouring the Yahoo! boards to kind of seed this listing. One major thing to keep in mind is that while each of the following have been known to be compatible solutions you need to check the portable router's owners manual to make sure that modem is compatible with the router. If you have any experience with one please edit this page.
This list is not all inclusive and I went thru a few months of postings at the IRLP site and reported the ones that I saw. This also is not taking into account anyone who may be using 4G devices, personal cell phones or non standard 3G modems using VPN's or Tunnels to another point on the internet, those situations are outside of the scope of standard operations here on IRLP. - K0KAD