What are the famous tourist spots in Italy?

We had a trip to Venice, Florence and Rome last year.
Our objective was to cover as much as possible in limited possible budget.
Here is the list:
You can check full details at http://travelextracts.com/content/eurotr... where we have posted our day wise plan.
Venice
1.Academy Gallery (Gallerie dell'Accademia)
2.Bridge of Sighs
3.Correr Civic Museum (Museo Civico Correr)
4.Doge's Palace (Palazzo Ducale)
5.Grand Canal
6.Naval History Museum (Museo Storico Navale) & Arsenale
7.Rialto Bridge (Ponte di Rialto)
8.Rialto Market
9.Saint Mark's Basilica (Basilica di San Marco)
10.San Rocco (Scuola of St. Rocco)
11.St. Mark's Square (Piazza San Marco)
Florence
1.Ponte Vecchio
2.Uffizi Gallery (Galleria degli Uffizi)
3.Basilica di Santa Croce
4.Duomo - Cathedral of Santa Maria del Fiore
5.Duomo Museum (Museo dell'Opera del Duomo)
6.Galleria dell'Accademia
7.Giotto's Bell Tower (Campanile di Giotto)
8.Medici Chapels (Cappelle Medicee)
9.Piazza del Duomo
10.Piazza della Signoria
Rome
1.Borghese Gallery (Galleria Borghese)
2.Capitoline Museum (Museo Capitolino)
3.Colosseum (Colosseo)
4.Imperial Forums (Fori Imperiali)
5.Palatine Hill
6.Pantheon
7.Roman Forum (Foro Romano)
8.Spanish Steps (Piazza di Spagna)
9.Trevi Fountain (Fontana di Trevi)
10.Villa Borghese
11.Castel Sant' Angelo
12.Vatican Museums
13.Vatican City
14.Sistine Chapel (Cappella Sistina)
15.St. Peter's Basilica (Basilica di San Pietro)
16.Barberini Palace
17.Circus Maximus (Circo Massimo)
18.Ostia Antica
19.Palatine

You can find more details about each of these here:
Venice: http://travelextracts.com/content/venice...
Florence: http://travelextracts.com/content/floren...
Rome: http://travelextracts.com/content/rome-a...

Also you can read about our experience about staying here:
Venice: http://travelextracts.com/content/venice...
Florence: http://travelextracts.com/content/floren...
Rome: http://travelextracts.com/content/rome-a...

Venice - I think this is number one for Italy. Who wouldn't want to ride the "candola" (forgive the spelling).

Vatican - I think this is another major tourist attraction.

Rome -
Collosseum
Vatican City
Ancient Ruins

Naples -
Isle of Capri
Mt. Vesuvius

Pisa -
Leaning tower

Venice -
Canals

Northern Italy -
Italian Alps (Turin)

Islands -
Sicily
Malta

Rome - the Colosseum, the Trevi Fountain, the Spanish Steps, the Vatican Museum - the Sistine Chapel, the Pantheon, Piazza Navona...

Also outside of Rome:
Venice
The Amalfi Coast / Sorrento.

Venice- museums+ canals+St Mark's Square
Florence- museums+churches
Rome+Vacitan- Roman ruins+Churches+Museums

Rome (you could spend months there by the way but here's the main sites)- Vatican city, Pantheon, Trevi Fountain, Spanish steps, Piazza Di Navona
Venice- Burano Island, Murano Glass Factory, Gondola ride,St Marks Square, Dodge Palace
Florence- Statue of David
Asissi- Church of St Francis of Assisi
Milan-shopping!!
Pisa-leaning tower

The Vatican City
The Catacombs
All the ancient ruins of Rome
All the beautiful fountains
Venice
Torino (the Ferrari Factory)
Milan
Pisa
Florence
Too many Churches, Forts, Museums , too mention
Genoa (home of Columbus)
You need to read about Italy before you go. There are so many things to see and do.

It is difficul to answer to your question.
In italy there are many beautiful city and any of them have one or more interestin things to visit.
Baueutiful city thet i can suggest you to visit are
Turin (my city)
Venice
Florence
Rome