What are you recommended to see in Delhi?

I'd suggest staying around Connaught Place (CP) which is quite central. From here you will be close to Delhi Junction (main railway stn) in case you are also planning on taking the fast train to Agra.

From CP, you will be close to the Red Fort, Chandni Chowk (the big bazaar), Jama Masjid, and walking distance to India Gate and Rashtrapati bhavan (official residence of the President of India) and surrounding areas. You will also be a cab ride or metro away from the Lodhi Gardens, the Qutb Minar and Humayan's tomb (a precursor to the Taj).

I am traveling to Delhi in Dec and am planning on staying at the Le Meridien around CP. You can find additional hotels around CP and check for their ratings on TripAdvisor.

I would recommend you to make the most of your visit to Delhi by vising places which I have listed below:

1. Red Fort
Delhi's most famous monument, the Red Fort, stands as a powerful reminder of the Mughal emperors who ruled India. Its walls, which stretch for over two kilometers (1.2 miles), were built in 1638 to keep out invaders.
Entry Cost: Foreigners, 250 rupees

2. Jama Masjid
Jama Masjid is another marvelous treasure of the Old City, and is the largest mosque in India. Its courtyard can hold an incredible 25,000 devotees. The mosque took 13 years to build, and was completed in 1650. A strenuous climb to the top of its southern tower will reward you with a stunning view across the rooftops of Delhi. Be sure to dress appropriately when visiting the mosque or you won't be allowed in. This means covering your head, legs and shoulders. Attire is available there.
Entry Cost: Free, but a camera fee of 300 rupees applies.

3. Chandni Chowk
Chandni Chowk, the main street of old Delhi, is a shocking contrast to the wide, orderly streets of New Delhi. Cars, cycle rickshaws, hand-pulled carts, pedestrians, and animals all compete for space. It's chaotic, crumbling and congested, but completely captivating as well. As one of the oldest and busiest markets in India, its narrow winding lanes are full of inexpensive jewelry, fabrics, and electronics. For the more adventurous, Chandni Chowk is an excellent place to come to sample some of Delhi's street food. The renowned Karim Hotel, a Delhi dining institution, is also located there.

4. Swaminarayan Akshardham
A relatively new attraction, this massive temple complex was built by the BAPS Swaminarayan Sanstha spiritual organization and opened in 2005. It's dedicated to showcasing Indian culture. As well as the astonishing architecture of the pink stone and white marble shrine, the complex includes sprawling garden, sculptures, and boat ride. Allow plenty of time to explore it thoroughly -- at least half a day. Do note that cell phones and cameras are not permitted inside.
Entry Cost: Free. However, tickets are required to view the exhibitions.

5. Humayun's Tomb
If you think Humayun's Tomb looks a bit like the Taj Mahal in Agra, that's because it was the inspiration for the Taj Mahal's creation. The tomb was built in 1570, and houses the body of the second Mughal emperor, Humayun. It was the first of this type of Mughal architecture to be built in India, and the Mughal rulers followed it up with an extensive period of construction all over the country. The tomb is part of a greater complex that's set amongst beautiful gardens.
Entry Cost: Foreigners, 250 rupees.

6. Lodi Gardens
Lodi Gardens provides a serene retreat from city life, and is the place to come if you're feeling tired and worn out. The vast Gardens were built by the British in 1936 around the tombs of 15th and 16th century rulers.

7. Qutab Minar
Qutab Minar, the tallest brick minaret in the world, is an incredible example of early Indo–Islamic architecture. It was built in 1206, but the reason remains a mystery. Some believe that it was made to signify victory and the beginning of Muslim rule in India, while others say it was used to call the faithful to prayer. The tower has five distinct stories, and is covered with intricate carvings and verses from the holy Quran. There are also a number of other historic monuments on the site.
Entry Cost: Foreigners, 250 rupees.

8. Gandhi Smriti
Entry Cost: Free.

9. India Gate
The towering archway of India Gate at the center of New Delhi is a war memorial, built in memory of the Indian soldiers who lost their lives fighting for the British Army in World War I. At night it glows warmly under floodlights, and the gardens that line its boulevard are a popular place to enjoy a warm summer's evening.
Entry Cost: Free.

10. Bahai (Lotus) Temple
Entry Cost: Free.

I'm considering a trip to India. Since Rick doesn't have a guide for that country :( can someone recommend a good one. Over the years I've tried Fodors, Frommers, and Lonely Planet. I loved my Frommer's guide to Japan a few years ago, but they don't seem to be printing any more (at least I didn't find any Frommers at Barnes and Noble recently)