Forgive me if this is common knowledge, but I can't find this plan on their website at all. If someone has a link to it, could you post it? Maybe it's just an in store thing?
They still have it as I just signed up with this plan last week. Scroll to the middle of this link and you'll see the $30 plan under the $3/day prepaid plan. http://prepaid-phones.t-mobile.com/prepaid-plans
If you already have a phone and a SIM card activation kit you can use this link to activate the $30 plan. It will ask you which plan you want during the activation process. This is how I signed up with the plan. https://www.t-mobile.com/shop/plans/ActivateCodes.aspx
Oh, no worries as I had a tough time finding it myself until I found an old thread about it on here. It's a great deal for those people that have good coverage in their area. Unfortunately I'm finding out that T-Mobile isn't that great here and there are many areas that still have only EDGE and even a spot with No Service.
I had my doubts about their coverage in my area, but have been using an iPad with a T-Mobile sim and have been surprised with the coverage. Still nowhere as good as Verizon, but I didn't expect it to be. T-Mobile's a contender for my business.