I also wanted to have the same interface than wordpress theme search, but the only things i have tried are :
Multiple category plugin and filter by tags plugin…
For my website talking about how to pay online, I wanted to make a rapid sarch for customer: search a payment method + a category of sites. Example i want all shopping site which accept Moneybookers , or Forex site with Neteller.. Example here : payer en ligne
If you have news…
