I've been swatching all weekend, looking for the right combination of yarn and needles for Oat Couture's Celtic Cardigan.
I started out with some Cascade 220 in dark green. Not only did it feel like armor, but it was way too dark to appreciate the cables and stuff.
Bev (the owner) at Ewe'll Love It (my LYS) suggested I try a DK weight instead. Enter Silky Wool.

With the suggested needles, it was a bit too big (and floppy) pre-wash and block. I'll let you know in a day or two if blocking shrunk it appropriately.
I also tried Jaeger's Matchmaker Merino DK. I'm thinking about the color "Putty". My LYS didn't have any Putty in stock, so I bought a ball of white to swatch and practice with.
This one was exactly on gauge pre-washing/blocking. I mean exactly! I soaked it in warm water and Eucalan for about 10 minutes and layed it out to dry. It definitely stretched in the wetting. I mushed it back into a semblance of gauge (stitches per inch were OK, I can't mush the rows down enough, but I'm less worried about that).
Here it is before washing:

I'm going to try both the Silky Wool and the Matchmaker on the next smaller needles and see how that goes. One thing I notices is that my cables seem to be very elongated compared to the picture of the finished sweater. Any suggestions for how to keep my stitches loose enough to not be fighting for every twisted stitch, while still maintaining a compact row gauge?
I also did a swatch for the Fir Cone Shawl from the Folk Shawls Book. The Frog Tree Alpaca Sport yarn that I ordered last week did arrive. I selected color #31. It's a rather muted slate blue. Looks great with jeans. Here's my test swatch of the inner square pattern.

The way the increases and decreases work together causes a big "bulge" toward the wrong side, as you double-decrease the first time when coming onto the alternate "fir cones". But blocking flattened it out. The trick seems to be when you slip 1, then knit 2 tog, then pull the slipped stitch over, you have to be very careful to pull the slip stitch as gently as possible so as not to create extra bulk there.
I'm still working on Mike's seed stitch sweater too. It's perfect for car-knitting and tv-knitting. Knit, purl, knit, purl, knit, purl, knit, purl.........................