Top things to do in London with visitors?

I know there are soooo many amazing things to do in London but I just want to hear from other people what their favorites are! I will be playing tour guide with my parents who have never been here. We definitely will do the top touristy things (Buckingham Palace, Big Ben, West Minster, go on the London Eye, etc). I'd also like to go on a boat tour and possibly to a nice market (maybe Borough Market). My mom really wants to go to Harrod's so we will go there and to afternoon tea at Brown's Hotel.

I'd love to hear everyone's suggestions or favorites! This will be helpful not only for my parents being here but just for future trips to London. (I live about in the north "burbs", Welwyn Garden City). 

If you're going to do all the main touristy things, my advice is to get one of those passes that gets you into a bunch of different venues for a discounted rate. Otherwise, you will pay through the nose! When we were there a few weeks ago, we paid 16 quid each at each location (St Paul's, Westminster, and the Tower of London). 32 x 3 is a lot of money! 

Buckingham Palace is probably a waste of money and also the queue is insane.
You can save the £15 entry fee to Westminister Abbey if you attend a service (also they're gorgeous, especially if the choir is singing)

Afternoon tea at Harrods gets booked up months in advance, so book soon if you want to go there.

Also there's lots of threads on this, so you might want to do a search as I know I've listed all this several times before.

Afternoon Tea ANYWHERE in London is a treat, try a few of the hotels in the city.

I took my US DH on a Jack The Ripper tour when he once visited he got a real kick out of that, it's interesting, historic and there's a few cool pubs en-route .

The Tower is a must see.

I  think that the Orangery at Kensington Palace is a great place to have Afternoon tea, it's not as crazy expensive as everywhere else, it's in Hyde Park and in a Palace, my FMiL really loved it.

http://www.afternoontea.co.uk/index.php?option=com_content&task=view&id=36&Itemid=3

I can't do the Jack the Ripper tour, it went past my old house so it always seemed really silly but other people probably wont have this baggage!

I think the Hairy Goat tour is really fun if they're into photography- http://www.hairygoat.net/

I second cheesebiscuit's suggestion -- the tea at Orangery at Kensington Palace is lovely!  Tea at the Ritz is also amazing but naturally has the price to match.  Or Fortnum and Mason is fabulous as well... sorry, I love tea. 

If you like tours, you can go around Parliament for free.  Though you do have to request space in advance from your MP and it does book up quickly. 

I LOVE Nottinghill and Portobello road! Go on a Saturday. Go to Hummingbird's bakery, if the queue isn't miles long, and have a slice of cake or a cupcake. YUM! Nearby Nottinghill is Ladbroke Grove and Westbourne park, not for everyone, but a friend that was visiting me loved exploring the canals.

If you love views, go to Cutty Sark (DRL) or Greenwich station on the national rail in Greenwich for a beautiful view of Canary Wharf. Go have a picnic in Greenwich park on a sunny day. It's absolutely lovely.

Speaking of gardens, go to Kew Gardens near Richmond.

high tea was something! i loved the luxury of it because anymore, everyones always rushed.

i had my high tea at the relaxing resturant in the british museum.

Do the museums! (if your into that thing) and best of all free entry. But slip a quid or so into the dontation boxes if you can spare it. My favorite is the History Museum. Just the incorporation of all kinds of animal and plant life into the building took my breath away. Literally the gargoyles are dinosaurs and mammals... and THE SQUID! as to see it.

i've also really enjoyed the hop on/off bus tours. We did the red company (cant think of the name) but we got a free journey on the clipper water taxis on the river. we spent an afternoon in Greenwhich and had a BLAST. the 30 min water taxi ride takes you by a lot of the landmarks of london on the river.

I second the recomendations for portobello road. Any markets will be amazing and a tactile expierence that will be enjoyed.

Kew Gardens was huge but the houses were amazing if your into nature and flowers and such.

my favorite place to be was one close to our hotel. On the albert embankment there is a boat that is docked right infront of the Park Plaza hotel. I think it's called the Thamis Dock. It's an old boat thats converted on the inside and out to be a bar. They had some live music and we sat on the patio and just watched the traffic go buy. If you get the right seat, you can sit and look down the thames at the london eye, big ben and the hustle and bustle of the traffic crossing miles away.

Everyone says Buckingham Palace isn't worth the time or bother but, even though I was born in the UK, I've never been and would love to!

The thing with the London Eye - if you are afraid of heights - as I am - it lasts like 30 minutes or something, with no way out.

The thing with the London Eye - if you are afraid of heights - as I am - it lasts like 30 minutes or something, with no way out.

My husband wouldn't go on it for that reason, so I had to go solo.

I second the suggestion for the Jack the Ripper tour! I have done it a few times, with different visiting friends and relatives. It's always a good one. I also recommend the London Eye. I have a Merlin annual pass, so I get on there for free. I have been on 5 times minimum!

I have been inside Buckingham Palace, and it is interesting, but when friends visit we usually just go to the front and watch the changing of the guard.

Recommend one of the hop on/hop off bus tours, we did the Big Red Bus Company, if you book online in advance it's cheaper. You also get a river cruise as part of the tour.
Westminster Abbey is stunning, thought it was worth the entrance fee, so much history. St Pauls Cathedral also.....we ended up in here during a service.
Tower of London is worth seeing. The just wander past Parliament down past Downing St etc.
If you are interested in WW2, then I recommend Churchill's War Rooms - the underground rooms where he spent much of the war, that's in Whitehall....also the Imperial War Museum. There is also a new attraction called The Blitz, supposed to recreate what that was like.....but DW wasn't bothered about seeing it!
Definately recommend going to Harrods just for the food halls.....DW couldn't believe I was taking her to see food halls....until she saw it and insists on taking everyone there now!

Can be expensive, but there's nothing like a West End play. Find one that would be of special interest to them. Here's an A-Z listing of current shows: http://bit.ly/fgdlKe
 
The first show I ever saw here was Chitty Chitty Bang Bang and it was amazing!

Seconding the Imperial War Museum! I go every time I'm in London, sometimes multiple times. It's near Elephant & Castle though, so not really very close to anything else interesting.

Tower of London is pricey but worth it for the Beefeater guides.

All of the walking tours I've been on in London were fantastic, especially for being taken off the beaten path and getting ideas for things to do on my own later. londonwalks.com has some good ones and the guides are always witty and funny.