Several ports along the coast south of Rome -- Anzio, Terracina, San Felice Circeo, Formia, and Naples -- have boat service to Ponza. Only Anzio, Formia, and Naples are connected with nearby train stations, making transit from Rome relatively uncomplicated.
Anzio is the nearest point of departure from Rome (62km/39 miles, 1 hr. by train or car). From Anzio, Caremar (www.caremar.it) runs ferries to Ponza from mid-June to mid-September (1 hr., 45 min. each way; 19.20€). Vetor (in Anzio at Via del Porto Innocenziano 40; tel. 06/9845083; www.vetor.it) operates hydrofoils year-round (weather permitting); the journey takes 1 hour, 10 minutes and costs 27€.
From Terracina (a bit south of Anzio), Navigazione Libera del Golfo (in Terracina tel. 0773/725536; in Ponza tel. 0771/700710; www.navlib.it) runs fast jets to Ponza from April to September (75 min.; 19€). SNAP & SNIP (in Terracina tel. 0773/790055; in Ponza tel. 0771/820092; www.snapnavigazione.it) runs jets (70 min.; 15€) and ferries (2 hr., 30 min., 10€) between Terracina and Ponza, also from April to September only.
The closest port to Ponza is San Felice Circeo, a popular seaside resort within the Parco Nazionale del Circeo, though well away from the train lines and highways that connect Rome and Naples. From San Felice Circeo, Linea Talamata (tel. 0773/661423; www.talamataviaggi.it) runs ferries (1 hr.; 18€; daily mid-June to mid-Sept; weekends only mid-May to mid-June and mid-Sept to Oct).
Farther south on the Italian coast, the port of Formia (167km/104 miles from Rome, 101km/63 miles from Naples) is connected to Ponza year-round by Caremar (in Formia at tel. 0771/22710; www.caremar.it), with regular ferries (2 hr., 30 min.; 10.80€) and hydrofoils (80 min.; 18€), and by Vetor (in Formia at Banchina Azzurra; tel. 06/9845083 [central info and reservations line]; www.vetor.it) hydrofoils (70 min.; 24€).
From Naples, Snav (tel. 081/4285555; www.snav.it) runs hydrofoils (July and Aug only) to Ponza, stopping at Ischia-Casamicciola and Ventotene along the way. Naples-Ponza takes 2 1/2 hours and costs 40€. (Note that this service is from Naples's smaller, more elegant Mergellina harbor.)
For travel between Ponza and Ventotene, a few of the companies listed have boat connections in July and August only, although service is rather limited (about three boats per week for each company). Navigazione Libera del Golfo jets take 1 hour and cost 13€. SNAP & SNIP jets take 1 hour and cost 10€. Snav's hydrofoils (July and Aug only) link Ponza and Ventotene (20€).
You'll need your feet, a bus ticket, and a boat to discover the best of Ponza. Around town, walking is the only way to go, and when the island's best beach, Chiaia di Luna, isn't closed for safety reasons, you can reach it on foot from town. The rest of the island is long and thin with only one main road, which is served by Autolinee Ponza buses from Ponza port (Via Dante; tel. 0771/804470; 1€ one-way; 6:30am-3:30am in summer). But because much of Ponza's 22km (14-mile) coastline and its most alluring coves are only accessible by sea, you really need to rent a small motorboat (gozzo, gommone) to do the island justice. More than 20 different companies, at most of the major coves and beaches, rent boats to tourists, but Diva Luna (Spiaggia Sant'Antonio, just north of the ferry landing; tel. 338/2347608 or 0771/809906; www.divaluna.com) is by far the best, with friendly service and fast, new boats (gommoni from 50€-110€ for a full day; 30% discount for a half-day). In a day of calm seas, you can go all the way around Ponza as well as zip over to nearby Palmarola, stopping for a few swims and pausing for a picnic along the way. Be sure your boat has a sun shade (tendalino), and if you're going over to Palmarola, a slightly larger motor will come in handy. Organized island-circumnavigation tours are also offered by a number of outfitters at the port. Scooters and cars are also widely available for rent on Ponza, but they're more of a liability than convenience here.
The Pro Loco is at Molo Musco 2 (tel. 0771/80031; www.prolocodiponza.it). They can furnish you with island maps and provide information about nontraditional accommodations options like room rentals.
The banks San Paolo IMI (Corso Pisacane; tel. 0771/820554) and Monte dei Paschi di Siena (Corso Pisacane; tel. 0771/80654) both have ATMs. The carabinieri are at Molo Musco (tel. 0771/80130). The main pharmacy, Farmacia Mazzella, is at Piazza Pisacane 9 (tel. 0771/80708); a medical clinic and the Guardia Medica are in Località Tre Venti (tel. 0771/80687). The post office is in Piazza Pisacane (tel. 0771/80672).