I've had several questions on this topic, so I've decided to list a number of yarn substitutions for the Trendsetter Journey yarn which was used for my Aran Wrap in Vogue Knitting Fall 2008. This is a lovely, 100% alpaca yarn in beautiful heathered colors, but it does have the disadvantage of being quite heavy. I'm not talking about heavy as in yarn thickness, i.e. heavy worsted (which this yarn is, at a ball band gauge of 16 sts to 4"), but heavy as in just plain heavy, at only 55 yards to 50 grams. The construction and fit of the Aran Wrap means that it is really just a large rectangle of knitted fabric with sleeves, and the fronts either fall in folds or are overlapped. While this makes it a cozy layer on an autumn day, it also makes it potentially quite weighty.
When I swatched for this design, I actually used a worsted weight wool (Classic Elite Skye Tweed, if anyone is curious), but the VK editors chose to substitute a heavier (in both senses of the word) yarn. Personally, with careful swatching, I think one could go back to a medium worsted weight yarn, meaning a gauge of 17-19 sts to 4"-- but I'm not going to get into making recommendations for that here.
So here are some possibilities which have the same (or very nearly so) ball band gauge as the Journey. I've listed all of their weights per 50 grams to make them easy to compare, but if they are supplied in different sized skeins, the actual skein yardage and weight is also noted.
Adrienne Vittadini Trina, a merino wool/ microfiber/cashmere blend, 71 yds/50 gms. I'm currently using this for another project and like it a lot; I've had to frog small sections a couple of times and resurrect some of it once, and it has held up well. Shows stitches very nicely.
Valley Yarns Berkshire, 85% wool/15% alpaca, 71 yds/50 gm (141 yds/100 gms).
Reynolds Candide, 100% wool, approx 86 yds/50 gm (170 yds/3.5oz).
Berroco Peruvia, 100% wool, 87 yds/50 gm (174 yds/100 gm).
Cascade Eco Wool, 96 yds/50 gm (478 yds/250 gm).
And the lightest heavy worsted of them all: GGH/Rebecca Bel Air, 90% merino wool/10% nylon, at a whopping 143 yds/50 gm! Produced using "new spinning technology!!" If anyone uses this, I'd be very curious to see how it turns out; for a project like this, it certainly sounds good in theory.