metcarl: I am quite partial to Guinea Pig Market's fleece products. The company is unfortunately very backed up at the moment. It was never like that when I ordered from them in the past. To give you a sense of the timeline, I placed an order (reservation, actually) on November 20, and was contacted on December 29 to pay for it in order for it to go into production. My order has not shipped yet. The quality is top notch though. Very durable fleece blankets that have never leaked or failed me. They are heavy enough that I am able to vacuum them without them lifting off the floor.
I will caution that you may face delays with other sellers as well. When I learned that Guinea Pig Market was backed up, I placed an order with a company called Four Legged Luxuries (in addition to the order I placed with Guinea Pig Market). That order has yet to ship too, and the timeline has not been clear. Guinea Pig Market's reservation system at least gives you a sense of the timeframe, and you do not have to pay until the order goes into production. The verdict is out on Four Legged Luxuries, but I did find some really cute patterns on their site. I am looking forward to trying out their stuff.
For faster shipping, you could try Guinea Dad. I placed my first order there too, at the same time as the others. Guinea Dad was able to ship right away. They do not have the same variety in patterns or cuts (shapes), however, but I was happy having the immediate backup. (We expanded our cage recently, which caused the immediate need for some new fleece for the new space.) I like using their pee pads.
If you can wait, I would stick with your order from Guinea Pig Market. I think you will appreciate the quality of the product you will eventually receive.
Good luck!