KL Holiday Tips

On the whole, Journey Malaysia is the best website to get info on Malaysia and things to do, whether in the cities, islands or jungles. You can also book hotels and get tours from there. www.journeymalaysia.com

KL (within and around city centre)

Museums
Islamic Arts Museum is supposed to be very good (though I've never been there myself), also the National Art Gallery, Petrosains Musuem (in Twin Towers), National Science Centre, Rumah Penghulu at National Heritage Centre

Parks
Eye on Malaysia (Titiwangsa Lake), KL Bird Park (also a couple of other parks/gardens in the area worth dropping by if you're in the area)

Shopping
all the usual places - KLCC for high-end, Bukit Bintang for medium-high, Petaling Street (Chinatown) for fake goods, Central Market for souvenirs/cultural, Little India (Jl Masjid India) for Malay & Indian stuff, Brickfields (around KL Sentral main train station) for Indian food and clothes

Religious monuments
Walk around old city centre to Masjid Jamek, Sri Maha Mariamman Temple & Chinese temple opposite. This is all in the same area as Chinatown and Central Market, so if weather is good you could spend about half-day in this area just walking around.

There is a hop-on hop-off bus service which takes you to major tourist attractions in the city for about RM 40 per person. Might be worth doing that for one day, to get an orientation of the city and the major tourist attractions. It's called KL Hop-on Hop Off, and should be available at major hotels.
http://www.myhoponhopoff.com/
http://www.journeymalaysia.com/MC_kualalumpur.htm

Around KL (day-trips)

Batu Caves + Orang Asli Museum - definitely worth a day trip. Should just rent a taxi for the day and get them to take you to these two places.

Sunway Lagoon - big water theme park, probably fun for older kids and teenagers. There is also a huge shopping mall next to the theme park.

Fireflies in Kuala Selangor - this is an evening event, and only if weather is good. Hire a taxi to go out to Kuala Selangor (1.5 hours drive) and take a small boat cruise to see fireflies along the river. This is the only place in the world that you can see so many of them in the wild like this. If you dont mind eating chinese seafood, there is also a place where you eat seafood by the river.

Outside KL (1-2 nights' stay)

Fraser's Hill (Bukit Fraser) - nice cool place up in the mountain, abt 2 hours drive from KL. Old golf course if you're interested to play. Otherwise just a quiet place to relax, jalan-jalan and enjoy nature. Have to rent a car/taxi to take you there. http://www.journeymalaysia.com/MH_fraser.htm

Melaka (also possible for day trip) - historical city with a lot of monuments, museums, antique stores, abt 2 hours drive from KL. There are buses every hour from KL, very convenient for day trip4. Very good local food.

Makan

Malay
Kelantan Delights in KLCC. Also, for very good Nasi Lemak there are 2 places: AJ in Jalan Lumut next to Vistana Hotel and Puteri in Desa Sri Hartamas
Chinese (Halal)
Spring Garden in KLCC (price and taste ok, but not very good), Dim Sum at Mandarin Oriental (expensive but very very good, especially the durian pancake), Little Penang Kafe in KLCC or MidValley (my favourite - good food at reasonable price), Precious (upstairs of Central Market - great food, not too expensive)
Indian
Lots of places!! For Banana Leaf rice - Nirwana Maju in Bangsar from 12noon - 3pm, Roti Canai - Nirwana Maju from 8-11am, B'Sentral in Brickfields opposite KL Sentral. For Indian sweets, Jai Hind in Jalan Melayu, near Masjid India/Masjid Jamek (very famous!!)

Areas where you can find a lot of restaurants & good food:
Hartamas - many pubs and restaurants, one of my favourites is Souled Out (very popular and good value for money)
Bangsar - Delicious, Marmalade at Bangsar Village II, Sakae Sushi, Nirwana Maju, Devi's corner, La Bodega Deli & Lounge (one of my favourites for brunch)
Bukit Bintang area - lots of restaurant franchises/chains.
If you like Japanese food, the Japanese Buffet at Jogoya (4th floor Starhill) is really good value (RM 100 per person - all you can eat, with good quality and good taste). Also the area in the basement of Starhill has a lot of nice restaurants (Tarbush - middle eastern - is best value for money in the entire place), very nice to walk around even if you don't eat there.
If you really want to find more eating places, try www.friedchillies.com