My two favorites are Best Day Ever and World Travels. They're huge, so I've used them for single pages and for albums where I'm trying to stick to a handful of kits. The colors work well for scrapping males and females, and they're colors that seem to match my photos well. (Blue is probably the color I use most. I find myself not using the collabs that have a lot of pink. I'm the only one here who likes pink, and I rarely have photos that look good with pink kits.) Best Day Ever has an everyday theme, which is probably the type of page I scrap most, and I also do a lot of travel pages.
I don't post that many pages any more, but I did have one with Best Day Ever in the gallery.
