Certain rules of etiquette govern which type of gift is appropriate for a colleague. These conventions aren't set in stone; rather, they vary depending on the nature of the relationship and the reason for saying "thank you." Think about what type of gift feels right for you, and follow "green" gift giving strategies such as only purchasing something the recipient will use, or purchasing "experience" gifts instead. A tasteful, thoughful gift can fit just about any budget, and will be appreciated.
Few things brighten an office like a plant does. Potted flowers add instant cheerfulness to an office, and they can fit almost any budget. If you'd like to spend more, and you know the recipient has the space, a larger floor plant or another more lavish plant such as an orchid can be a wonderful gift. Or, for an environmentalist, a terrarium can bring some of the outdoors inside.
A decorative item like a vase is a tasteful gift for a professional colleague. You could choose an elegant glass vase, ceramic vase, or stone vase in any number of styles. If your colleague has an artistic flair, and you have a higher budget, you could look for an unusual abstract vase. If he likes antiques, you could look for a vase from a particular time period.
Restaurant Gift Certificate
While gift certificates are often too generic to make a good gift for a colleague, a gift certificate to a favorite restaurant--yours or theirs--is a thoughtful present. The restaurant should have food they would enjoy, and it should be a place that speaks well to your own tastes. Preferably, the gift certificate would cover a dinner for two people.
A Gift Basket
Gift baskets come in all shapes and sizes, fitting just about any colleague's tastes. Since most gift baskets appeal to a wide variety of people, they work well even when you don't know a colleague well. You could purchase or put together a basket filled with teas, coffees, jams, and baked goods, or a basket of fruits. Choose organic teas and fair trade coffees, as Planet Green suggests. Many people also enjoy baskets of bath products, filled with items they wouldn't usually purchase for themselves.
If a local museum is having a special exhibit, consider giving your colleague tickets as a thank you gift. Find out if you can get tickets for flexible dates, so your colleague can go when she chooses. Purchase two tickets so she can enjoy it with someone else.