I've been told sometimes you can get a club member with status to take you in as a guest.
I've also had a friend tell me, for example, in Santiago (SCL) he paid $30 to get in, which for a shower, wifi, and a buffet, was totally worth it for the day he was stuck in the airport.
Is there a website or something with an indication of what you can get into, if you don't have membership status, with costs, benefits and the like?
The best resource available, as has been mentioned in another answer, is loungeguide.net. It's coverage ranges from excellent to OK, depending on the part of the world you're looking at.
It's worth keeping in mind that Airport lounges are not necessarily as good as you might have been led to believe. Some are excellent, including the services you've mentioned, such as showers, wifi, sufficient food to be considered a meal, alcohol, etc. However many do not have these services - showers are uncommon in many parts of the world (eg, very few lounges in the US have them), food is often at best snacks (one American Airlines lounge I was in recently had biscuits/cookies, and nothing else), Wifi is normally provided, but sometimes it's just the free airport wifi.
Before spending money to access a lounge make sure you're aware of the specific facilities offered. Also be careful with what you're actually buying. Some airlines (eg, American) will allow you to buy a "day pass" that can be used at multiple lounges on the one day - useful if you're passing through more than one airport in that day, whilst other airlines (eg, United) only sell a single-entry pass that can only be used once at a single airport.
Outside of the US, paid access to airline-run lounges is rare, however there are frequently independent lounges that will offer paid access, but prices and services offered can vary widely.
You could also look at Priority Pass, which gets access to multiple lounges around the world. Priority Pass generally requires an annual fee and/or per-entry fees, however it is also offered as a free extra with some credit cards (although in the US this will only get you access to limited lounges). Lounge Club also runs a similar but more limited service - not surprising given that it's run by the same company as Priority Pass!
I'm not aware of one website which covers this comprehensively.
However, there is some information on guests and lounges generally for each of the major airline alliances:
Oneworld allow entry for one guest for Emerald and Sapphire members: http://www.oneworld.com/ffp/lounge-access/ (with exceptions for American Airlines lounges)
Star Alliance allow one guest for travelling in First Class or for Gold members: http://www.staralliance.com/en/benefits/lounges/lounge-access-policy/
Skyteam allow guests for Elite Plus members travelling internationally: http://www.skyteam.com/en/Why-SkyTeam/SkyTeam-Lounges/
(that's for departure lounges - typically arrival lounges are rarer and the entry policies are even stricter)
My personal experience is that policies vary - the above are the 'minimum', but some lounges may be more generous, particularly if the guests are family members, the lounge isn't packed with people, guests are dressed smartly, you ask nicely, etc.
loungeguide.net also maintains a fairly extensive list of lounges with details about facilities, entry policies, etc. For some of those there are details on what you can pay to get in.
Typically in my experience airline-branded lounges outside the US often don't allow you to pay for entry at all (although there are generic lounges, such as those operated by Servisair, that normally do). In North America, sometimes airline lounges do allow for paid entry, but costs can be steep (e.g. American Airlines Admirals' Club charge $50 for a day pass).
I don't think there's one single resource you can look at. There are various websites that give lounge information, but often with gaps or out-of-date information.
Instead, look up the website for the programs that interest you. They generally explain all the details of who can access, with what guests etc to non members, and what the lounges provide. Andrew has provided links to the main ones, have a review of those.
