Cap-sleeve dresses are a warm weather staple. When you work in a professional office, sleeveless might be teetering on the line of inappropriate. This little bit of sleeve lets you keep to a springtime/summertime silhouette while keeping things dress code friendly.
I also found this cowl neck dress in royal blue and charcoal. This striped Ralph Lauren shift is also a good choice. Tahari ASL also has a cap sleeve dress in jade that would be lovely for work, though it would benefit from a belt.
Plus-size? This Calvin Klein dress has a great neckline and comes in black or blue. Petite? Ralph Lauren offers a very similar dress to the Zara in the same bright blue. Tall? Ann Taylor offers a seamed sheath in colorblock of neutrals, also in petite and regular.