I am by no means a regular submitter to the magazines or for design team calls. But I have occasionally tried out for a team I thought would work for me, or submitted a layout I had on hand that fit a magazine call.
I think the main reason I don't submit consistently is that it can be a lot of work to hunt down all of those calls. Thankfully there are now two sites that do most of the work for you.
The first is a site called Design Team Calls.
Also now available is a section for challenges and contests that even has a list of prizes!
There is a premium membership known as the Design Team Calls Insider available but it's not something that I personally have found necessary. The site seems to have enough great resources without all of the "extras".
I have to say I am personally grateful to Susan's site, because this one was where I discovered the design team call for Crafting Ireland magazine. Since it is a newer magazine, I don't think I would have been aware of the call if I had not seen it on the Design Team calls site. :)
The second site is 100% free at this time. DT Calls is a simpler site that has a nice blog format on the home page with tabs for a list of current calls and challenges.
Both sites have Facebook pages which you can access from their home pages which is helpful!
So if one of your scrapbook goals is to be published in a magazine or find a design team position, these sites may be helpful to you!