Delphi has no shortage of lodgings; you can usually find rooms even in July or August. When tourists are few, you may be able to improve on the rates below. Still, if you want to be sure that you get a room in a specific price category (or with a view or a pool), it's best to make a reservation in high season. With the growing popularity of skiing Parnassus, fewer and fewer of Delphi's hotels close for part of the winter, but summer is still high season here.
In addition to the following options, we've had good reports of Apollo Hotel, 59b Frederikis (tel. 22650/82-244; fax 22860/82-455), and its sister hotel, Villa Filoxenia-Apollo (tel. 22650/83-114; fax 22650/82-455); Hermes Hotel, 29 Vasileos Pavlou and Frederikis (tel. 22650/82-318; fax 22650/82-639); Pan Hotel, 53 Vasileos Pavlou and Frederikis (tel. 22650/82-294), and its annex, the Artemis, 53a Vasileos Pavlou and Frederikis (tel. 22650/82-793; fax 22650/82-780). The little Odysseus Pension, 1 Isea (tel. 22650/82-235) has a garden and is a good budget choice (most rooms with shared bathroom).
Tip: If you want a main street room with a view, be sure to ask for a back room with a balcony that faces the Gulf of Corinth. You may not always see the water, but from your balcony you will almost always see the magnificent valley of olive trees that leads down to the Gulf -- and avoid the traffic noise of the main street.