You could always get ain aircard and pay a wireless provider for that type of connection, but its expensive. He other option is a wireless card as you have said, now i dont know for sure how truely good it is, but i bought a SMC2862W-G thumbstick wireless adapter recently to use on my Music PC in the adjascent room to where my internet connection is, i did not want to run a cable through a wall, or leave it on the floor to trip over so i figured wireless was the route to go. Being a thumbstick type i was skeptical, i figured the range would be very limited and it wouldnt pick up very much, being one room away i envisioned about a 75% signal, but i was suprised to see a full 100% signal strength, and i was picking up 5 OTHER networks in the area all at varying levels of signal, and i'm in a house in a neighborhood, not really near too many businesses, the nearest business has to be a good 800 - 1000 feet away, i was really suprised.
So, when i was thinking about getting my server back up and running, its a machine i use as a file server, web server, and ventrilo server, i wanted it in the basement, but the basememnt is finished (i live in a split level) so again i didnt want to go to the great lengths of drilling holes etc to get a cable down there, so i bought another one of these adapters, i figured going all the way down to the basement i should get at least 50% signal seeing as how well i picked up with one upstairs, and all the surrounding networks it saw. I was astonished to get about 90% (still in the "Excellent" range), on my own network, and still able to see one of the stronger outside networks, these things are amazing as far as range, and it was only $30!!!! I recommend this strongly.