Port, a dessert wine ``invented'' by the British, is a complicated topic. My personal rule is to stay away from Ruby, LBV, and Vintage ports. The value just isn't there, although I have about 1/2 dozen Vintage ports aging, so I might change my mind in 10 years when they're ready! It wasn't that long ago that Vintage Ports were affordable, but then the 90's wine boom put them largely out of reach of cheapskates like me.
So I drink Tawny port. It is basically regular port aged for 5+ years in a barrel, which draws out the color, making it "tawny". In return, you get sweet flavors of caramel, cinnamon, and cedar. And you don't have to age it, it's already been done! (In fact, you shouldn't age it.) Tawnies are tremendous when complemented with hard cheeses, nuts, pears, or sweets. Some say chocolate doesn't go well. Bah! On the site, check out the "Other" category for some ideas, looking over this year and last. I don't have port or dessert wines as a category.
All the major Portuguese Port houses make good Tawny. The 10-years are good (average time the wine spent in the barrel is 10 years -- the wines are typically produced by blending), but 15's and 20's tend to be better, especially if you like the flavors brought on by aging. I'm a nut for fruit in my wine, and I still feel this way. A great value is the Warres Nimrod; the Otima is easier to find but not as stirring. Try Porto Roche if you can find it.
The other great news is that Australia makes great bargain tawnies and similar dessert wines, in contrast to the small number of bargain dry wines available from there. An inexpensive place to start is the Benjamin Tawny or Yalumba Clocktower, both from Australia. Yalumba is a tremendous dessert wine producer, but it's just one of many.
When you get bored of Tawnies, look into Oloroso Sherries (from Spain) and Malmsey Madeira's (from Madeira Island of Portugal). These are typically much harder to find and gauge for quality.
In the San Diego area, great values are to be found at Cost Plus, San Diego Wine Company, and Trader Joe's (sporadically). Whole Foods has a good selection, but it's not always a bargain. Wine.com has a good selection of Tawnies at reasonable prices. See also port-wine.com and Oportowines.com.