Can condoms be used for masturbation? Or is that a waste?
The choice of whether or not to use condoms during masturbation is dependent partly on your goal and partly on your method of masturbation. Are you using a vibrator or dildo, or are you letting your fingers do the walking? Are you looking to be neat? Getting used to how the condom feels?
For those who use vibrators and dildos to pleasure themselves, condoms can be useful. For both men and women, a condom keeps the dildo clean, which can help prevent infections when a toy is shared, or prevent re-infections in the same person (whether the infection is sexually transmitted, or simply a run-of-the-mill infection, like a yeast infection). Condom use is especially important for women who use dildos and vibrators for both anal and vaginal stimulation. Use separate condoms for each orifice, as moving directly from the anus to the vagina can introduce harmful bacteria into the vagina or urethra and lead to urinary tract infections (UTIs) or other complications (also check out Finger from anus into vagina — Okay? for more info).
If you're choosing to diddle manually, the use of condoms might be taking safer sex a little bit far -- unless you have an active infection that you want to keep covered. The main cause for concern would be the presence of HPV (human papillomavirus, a.k.a. genital warts) or herpes lesions on the genitals. It's a good idea to try to avoid touching HPV or herpes lesions until they've healed — if you do come into contact with any sores, wash your hands thoroughly post-action. Conversely, if you have a wart on your hand, you don't need to worry about passing it to your genitals; genital warts are generally caused by different strains of HPV than warts on other parts of your body.
Another possible reason for using condoms during masturbation would be to keep things neat and tidy during and after your solo-sexcapades. While condoms would work in this respect, many find that tissues, hands, bed sheets, underwear, and so on...work just as well. If you're a novice, using condoms during masturbation may help you get the hang of how to use them and how they feel — that way, during partnered sex, you'll be a prophylaxis pro.