I saved the image of this yellow t-shirt dress by See by Chloe (from the Cruise collection) when it was still online a few months ago. It's bright, casual and looked like such a fun, easy-to-wear dress for the summer. I never managed to see it in real life but it got me looking out for tee shirt dresses. 
I love the design of this Mr. Abbott dress. I don't quite love the pinkness of this dress, but it's such a cute design!
The design of this Marc by Marc Jacobs dress looks cute from the front but the hole at the back makes it not very practical for casual, everyday wear.
Urban Outfitters has these simple, short-sleeved dresses. They're even nice enough for a nice dinner or night out.
The other shirt dress I found on uo.com is this plaid shirt dress. The bubble shape at the bottom makes the dress feels less indie and more girly, which makes the dress easier to pull of because let's face it, not everyone can pull of plaid!
The black dress on Lily Donaldson looks like another versatile, day-to-night dress. I'll be looking out for this one on my next trip to H&M.
Another dress I'll be looking out for is this See by Chloe jersey dress. I really like the print on the top and I'm hoping to find it in this dress version, (although I'll be looking out for the t-shirt version too.)During my search for t-shirt dresses I've noticed that it's much harder this summer than last summer to find them. It probably means that t-shirt dresses aren't 'in' anymore but they're just so cute and easy to wear! Plus, putting on shirt dresses is arguably even more brainless than a denim and t-shirt combo!
Image Credit: www.shopbop.com, www.urbanoutfitters.com, www.activeendeavors.com, www.chloe.com, www.hm.com