I consider their ads to not be too obnoxious (you'll see some at the top of this page) and Google does a nice job of providing relevant ads for each page (I was happy to see the ads up as I write this are for anti-spam stuff), although sometimes they are a bit goofy - for instance, on my lunar eclipse page, they were serving up ads for some place that was selling lunar real estate ... although that IS arugeably relevant! ;-)
You can read their guidelines at the URL above, but it's really a nifty program for people like me since it is easy to setup and runs on autopilot - i.e. I highly recommend it for small-time website hobbiest's like me. You are not paid for impressions (i.e. people seeing the ads), but only if someone does a click-thru on the ad - but pls do NOT take that as encouragement to do so since publishers (such as myself) are specifically forbidden per the terms of services to encourage click-thru's. The TOS also says I can't discuss the earnings, but stuff like Christmas decorations and The Incredible HULK aren't exactly high-value keywords ... so lets just say on good days, I can "super-size it" at McDonalds! ;-)
Related to Adsense is Websense which allows you to place a Google Search Box on your web site. I've put this on a few pages where I think it might be helpful and you can find an example on my home page where I have a site-specific Google Search - the later is a handy way to find stuff on www.komar.org - heck, even I can't find it all! Again, there is a few pennies/click-thru when you do this, but the main reason I use it is that I think it is just a darn useful tool - thanx Google for making available to the "little guys" like us.
I've spent a LOT of time over the years on all the stories/pictures/scripts/etc. on the web site, so my "hourly pay" for is probably on the order of a few cents/hour ... but I've enjoyed it and don't mind helping out people with stuff like the BBQ grill info and/or providing some entertainment for the random web surfer. Along those lines, read my copyright page at the bottom for more info which talks about how I don't mind sharing my stories/pictures/scripts/etc., but I have a problem with people that want to use it for their own personal gain - you know who you are!
I do get a chuckle out of ranking high in search engines such as Google for some funky stuff, so if you think my content is relevant, you are welcome to link to it ... although I'm not a Link Exchange type of guy. I've also applied some simple SEO (Search Engine Optimization) to these pages, but let me know if you think it takes away from the content. I'm a HUGE fan of good relevant content, and think that as Search Engines get smarter, they will get better at seperating the junk (especially from SEM's - Search Engine Manipulators!) from the jelly ... and hey, the bottom line is, did someone coming to my web site find what they were looking for (or at least get entertained) - I hope that is always the case.
The majority of people reading this will just gloss over all of the above, the minority will "understand" and realize I'm one of the "good guys" (or "white hats"), and unfortunately a small number of folks will try to figure out how they can "use" my stuff/web-site for their personal gain. Good news is that I'm a "white hat" Sysadmin in my day job, so I have a fairly decent BS meter and can usually sniff this stuff out! ;-)
P.S. BTW, if not obvious, I'm a "fan" of Google and impressed not only by their technology, but their ability to take the "high road" and do "no evil" as they like to say - they have a pretty "white" hat in my book ... lets hope they don't turn to the "dark side" since that would be bad! Another one of their efforts I support is the Google Compute Project which uses idle CPU cycles on your PC to benefit medical research at Stanford.