For me, protein was always a big deal during my first trimester! If I didn't get enough I could hardly function and was so headachy & grouchy. So, in addition to what I usually ate, I packed a ton of protein snacks with me to work every day. Some of my favs:
-hummus with crackers/baby carrots/cucumbers (great recipe here)
-smoothie with protein powder
-I'd make a bunch of chicken breasts or tenders to keep in the fridge and snack on them throughout the week
-Also, this page has a wealth of info on it.
If you are looking for more general food/health info, I also really liked The Natural Pregnancy Book.