New Baby - $50

Wedding - $85 (average according to the Association of Bridal Consultants)
How much you spend on a wedding gift should be determined by (1) how close you are to the happy couple, and (2) your budget. The amount you believe has been spent on the wedding itself is not a factor.
  * 20% of your total on the engagement present ($30)
  * 20% of your total on the shower gift ($30)
  * 60% of your total on the wedding gift ($85)
  (If you're only invited to the shower, then spend the extra 20% beefing up the wedding gift.)

Gift Cards:
Why Gift Cards Are a Crime Against Christmas | Money.com
Researchers have found that when people are given "play money" like gift cards, they're more likely to spend it on stuff they don't need. In fact, they're more likely to overspend. CEB Towers found that 65% of gift card users spend 38% more than the value of the card.

Christmas gift certificate:
$10-$50

Links:
8 Gift-Giving Etiquette Questions - International Business Protocol and Social Etiquette
Other gift page here
The Etiquette of Exchanging Holiday Gifts in the Office! - Blogs - Mix 92.9 - Your Life. Your Music - Nashville, TN