I have a D-Link router of the 2.4 gHz type. It supports 802.11b and I use it for all of the laptops I repair and test. I occasionally want to push the signal to the other end of the house, and I chose to do this, rather than buy a new add-on antenna.
Step 1: Getting Started...
I chose to keep the D-Link and cannibalize the Linksys for two reason, the first being that the Linksys uses a weird propietary 50-pin header to connect the card to the motherboard of the router. The second is that the D-Link uses a mini-PCI card as the receiver. I have a future use also, and this will make an upgrade easier, by far.
I also note the mini-PCI actually HAS two antenna inputs soldered on the card. The second one terminates in a little strip of metal that is stuck to the inner side of the case with double-back tape.