I agree with FAQ that it is a great idea to tailor your resume to a specific job that you are applying to when possible. When it isn't, having a good general resume is next best.
I think the first rule of resume's is that they should only be one page- unless you have cured cancer and built a better mousetrap! It doesn't have to cover everything you have ever done. You want it to convey enough about you and your skills that the employer wants to interview you and that is where you can really sell yourself.
I disagree with bonacker about the dates of your employment. I think you should definately put them on the resume, otherwise the employer is going to wonder what's up. You should expect that an employer will ask why you left each job, and have an answer prepared, it happens in most interviews no matter how long you had been at a job. It's best not to dump on a previous employer too much, but it is reasonable to talk about the opportunity for new skills at a new job, or moving to a job that paid more, or explaining that there was no room for advancement at a position. It is great if you can provide the name of a refence from an employer. (Usually good to check with the reference first).
A good resume needs to be easy to read and in a format that isn't too fussy. If I were you, I wouldn't put an objective on the resume. Unless you have a really specific objective, it is just wasting space, and most employer's don't really expect it. If it is the kind of job that requires a cover letter, that is good place to put this kind of info.
If you put an email on the resume, make sure it is professional, even if you need an additional yahoo or hotmail account. Hotpants.com can turn some employers off.
I would go with a nice three heading resume:
Name
Street
City
Telephone
Email
EXPERIENCE (bold)
Beagley Lawn Care, Kansas City, MO, date
(your description is good, did you work without supervision, were you responsible for supervising anyone or directing work flow among co-workers? Don't minimize your experience by saying "some" bookeeping experience).
Wackenhut Overland Park, city, state, date
were you bonded? add job description
Firstline, city, state, date
Sounds like you were responsible for judging security risks, diffusing tense situations, managing passenger flow, and honed decision making skills under time contraints.
Amity Woods Animal Hospital, city, state, date
(Move the weekend kennel manager to the front- supervising six people is an excellent skill!)
Animal Clinic...., city, state, date
(Emphasize your lab skills, mention specific equipment- sounds like these could be transferable)
Claycomo....., city, state, date
EDUCATION (bold)
Maple Woods Community College, city, state
Fall Semester 2002
Full name of high school, city, state
Diploma, (date received)
(If you played sports or were in band or were on honor roll or in plays- I think it is fine to mention here. Sometimes people interview you b/c they have something in common with you)
SKILLS (bold)
Typing Speed 55 wpm, Multi-line phone system, Microsoft Word, Excel, Quick Books, Internet, valid driver's license (Add in specific lab/medical equipment if relevant to the job you are applying for)
Add "References available upon request" to the bottom if it is true. I would leave off your Summary of Skills section.
To me it looks like you have some really good experience- keep your skill set in mind and sell yourself- finding a job is a job in and of itself. Good Luck