I'm not sure if you've done this in the past, but would you mind explaining how to get clients in the "old - or new-fashioned ways without a marketplace site"?
You network. You build relationships. You go to meetups and meet interesting people, swap connections, swap leads. You get strong introductions, you follow up, you build client relationships. They like you, they trust you, they want to do business with you, and they're willing to pay 4 or 5 figure sums for the privilege because you sell them more than work: you sell them peace of mind.
http://swombat.com/2011/2/25/kevin-mcdonagh-how-to-attend-a-... also proposes an approach to get leads from conferences (and despite the apparent machine-gun methodology, I'd like to qualify this article by saying that Kevin is an incredibly chilled out, laid back, friendly kind of guy).
All of the above, plus building an online presence in your area of choice. It is both a good way to make weak ties that turn into strong ties, and a good way for folks to find you when you're not actively networking.
Blogging and community participation (HN, etc) is my best source of consulting leads next to personal recommendations (and it is often a friendcatcher which caught the person doing the recommending).
"you sell them more than work: you sell them peace of mind."
This is the key to freelancing in general, as my father always tells me.(freelance photographer in the Middle East for almost 40 years: http://gustavoferrari.com/).
Whether it's online or off, if you can convince your clients that you can get the job DONE, with no excuses or delays, they will come back again and again. They want to be able to send you work, and forget about it, confident that you will come through.
Currently the shortest path that I can see is to go deep into iOS or Android programming, write a program or two, publish them in the respective app store, build a basic website to promote yourself (i.e. make an online portfolio i.e. just describe the programs you wrote).
Then go after iOS and Android gigs. Currently demand is vastly greater than supply and both platforms are growing, so it's likely to be true for some time.
http://swombat.com/2011/2/24/paulina-sygulska-how-to-network... is a great article on how to network.
http://swombat.com/2011/2/25/kevin-mcdonagh-how-to-attend-a-... also proposes an approach to get leads from conferences (and despite the apparent machine-gun methodology, I'd like to qualify this article by saying that Kevin is an incredibly chilled out, laid back, friendly kind of guy).